US20010041240A1 - Optical recording medium, recording material, method of producing optical recording medium, and optical recording, reading and rewriting method - Google Patents

Optical recording medium, recording material, method of producing optical recording medium, and optical recording, reading and rewriting method Download PDF

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US20010041240A1
US20010041240A1 US09/821,204 US82120401A US2001041240A1 US 20010041240 A1 US20010041240 A1 US 20010041240A1 US 82120401 A US82120401 A US 82120401A US 2001041240 A1 US2001041240 A1 US 2001041240A1
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Prior art keywords
phase
recording material
composition
change
pseudo binary
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Inventor
Kazunori Ito
Eiko Hibino
Makoto Harigaya
Takashi Hibaguchi
Hajime Yuzurihara
Nobuaki Onagi
Hiroko Ohkura
Katsuhiko Tani
Noriyaki Iwata
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Ricoh Co Ltd
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Ricoh Co Ltd
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Assigned to RICOH COMPANY, LTD. reassignment RICOH COMPANY, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HARIGAYA, MAKOTO, HIBINO, EIKO, ITO, KAZUNORI, IWATA, NORIYUKI, OHKURA, HIROKO, ONAGI, NOBUAKI, SHIBAGUCHI, TAKASHI, TANI, KATSUHIKO, YUZURIHARA, HA JIME
Publication of US20010041240A1 publication Critical patent/US20010041240A1/en
Priority to US10/356,136 priority Critical patent/US6884487B2/en
Priority to US10/976,061 priority patent/US20050058055A1/en
Priority to US11/410,791 priority patent/US7364781B2/en
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    • 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
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/0045—Recording
    • G11B7/00454—Recording involving phase-change effects
    • 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
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative 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
    • G11B7/26—Apparatus or processes specially adapted for the manufacture of record carriers
    • 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
    • G11B7/26—Apparatus or processes specially adapted for the manufacture of record carriers
    • G11B7/268—Post-production operations, e.g. initialising phase-change recording layers, checking for defects
    • 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
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
    • G11B2007/24302—Metals or metalloids
    • G11B2007/24308—Metals or metalloids transition metal elements of group 11 (Cu, Ag, Au)
    • 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
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
    • G11B2007/24302—Metals or metalloids
    • G11B2007/2431—Metals or metalloids group 13 elements (B, Al, Ga, In)
    • 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
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
    • G11B2007/24302—Metals or metalloids
    • G11B2007/24312—Metals or metalloids group 14 elements (e.g. Si, Ge, Sn)
    • 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
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
    • G11B2007/24302—Metals or metalloids
    • G11B2007/24314—Metals or metalloids group 15 elements (e.g. Sb, Bi)
    • 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
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
    • G11B2007/24302—Metals or metalloids
    • G11B2007/24316—Metals or metalloids group 16 elements (i.e. chalcogenides, Se, Te)
    • 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
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
    • G11B2007/24318—Non-metallic elements
    • G11B2007/24322—Nitrogen
    • 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
    • G11B7/2533—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 resins
    • G11B7/2534—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 resins polycarbonates [PC]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/21—Circular sheet or circular blank

Definitions

  • the present invention relates to an optical recording medium comprising a recording layer which is capable of writing information therein, reading written information therefrom, and rewriting written information therein.
  • the present invention also relates to a recording material for use in the recording layer of the optical recording medium.
  • the present invention also relates to a method of producing the optical recording medium.
  • the present invention also relates to a method of writing information in the optical recording medium, reading written information therefrom, and rewriting written information therein.
  • phase-change optical recording medium which utilizes the reversible phase changes between a crystalline phase and an amorphous phase thereof.
  • phase change optical recording media in which an Sb-Te recording material and an Ag-In-Sb-Te recording material are used, and have disnnavpred that the phase-change optical recording media using these recording materials have excellent characteristics, for example, in terms of C/N, erasing ratio, sensitivity, jittering, preservation stability, repeated writing and reading stability (hereinafter referred to as reading optical stability).
  • the optical recording media are being developed into DVD media.
  • the DVD media have a larger capacity, so that it is required that the response or correspondence to recording linear velocity (hereinafter referred to as the correspondence to recording linear velocity) be higher and that the beam spot on a drive side be small.
  • compositions in the shade area in the graph in FIG. 1 are used in the conventional CD media, in which graph the composition data are plotted with the recording linear velocity and the preservation stability (both with an arbitrary unit) as ordinate and Sb/(Sb+Te) as abscissa.
  • Such media have the problems that when the recording linear velocity is increased, the preservation stability and the reading optical stability deteriorate, and that when recording density is increased by reducing the size of the beam spot on the side of the drive, a sufficient sensitivity for use in practice cannot be obtained.
  • a second object of the present invention is to provide a recording material for use in the above-mentioned optical recording medium of the present invention.
  • a third object of the present invention is to provide a method of producing the above-mentioned optical recording medium of the present invention.
  • a fourth object of the present invention is to provide a method of writing information, reading written information, and rewriting written information in the above-mentioned optical recording medium or the present invention
  • the first object of the present invention can be achieved by an optical recording medium comprising a recording layer which comprises a phase-change recording material which is capable of performing a reversible phase change from a crystalline phase to an amorphous phase and vice versa by light irradiation of the phase-change recording material,
  • the recording layer being capable of writing information therein, reading written information therefrom, and rewriting written information by utilizing the reversible phase change of the phase-change recording material
  • d 1 which is the jitter increasing ratio of an initial writing mark
  • d ow which is a jitter increasing ratio of a 1000-times rewritten recording mark in conventional optical recording media
  • R is the ratio of a 5000th repeated reading jitter ⁇ repeat of the recording mark to a 1st reading jitter ⁇ 1 of the recordin mark, namely R is ⁇ repeat / ⁇ 1
  • the inventors of the present invention have discovered a recording material for use in the optical recording medium that makes d ow smaller than d 1 , that is, d 1 >d ow , in the optical recording medium as a result of their studies on the elements to be added to the recording layer, the fundamental structure of the phase of the recording material, the composition of the recording material, and the method of producing the recording layer.
  • the above-mentioned optical recording medium of the present invention has high correspondence to the recording linear velocity, and excellent reading optical. stability and preservation stability.
  • the recording material in the recording layer is a phase-change recording material which ie capable of performing a reversible phase change from a crystalline phase to an amorphous phase and vice versa by light irradiation of the phase-change recording material, so that writing information in the recording layer, reading written information from the recording layer, and rewriting written information in the recording layer can be reversibly performed.
  • the phase-change recording material comprise a pseudo binary composition, which has an NaCl-type crystal structure in the crystalline phase, wherein the pseudo binary composition is represented by Sb-TeM, comprising two portions, one portion being represented by Sb, and the other portion being represented by TeM, in which M represents a metal compound comprising at least Sb or Ge, provided that when TeM is Sb 2 Te 3 , the pocudo binary composition is a pseudo binary eutectic composition, and that at least one of the portions represented by TeM comprises Sb, and at least one of the other portions represented by TeM comprises Ge.
  • the pseudo binary composition is represented by Sb-TeM, comprising two portions, one portion being represented by Sb, and the other portion being represented by TeM, in which M represents a metal compound comprising at least Sb or Ge, provided that when TeM is Sb 2 Te 3 , the pocudo binary composition is a pseudo binary eutectic composition, and that at least one of the portions represented by TeM comprises Sb, and at
  • the total content ratio A of Sb and Te in terms of atomic ratio contained in the pseudo binary composition of the phase-change recording material be in a range of 0.80 ⁇ 0.97.
  • the contents of Sb and Te in terms of atomic ratio contained in the pseudo binary eutectic composition of the phase-change recording material satisfy a relationship of 0.65 ⁇ Sb/(Sb+Te) ⁇ 0.85.
  • the content ratio B of Ge in terms of atomic ratio contained in the pseudo binary composition of the phase change recording material be in a range of 0.01 ⁇ B ⁇ 0.07.
  • the pseudo binary composition of the phase change recording material further comprise as an additional element at least one element selected from the group consisting of Ag, In and Bi.
  • the pseudo binary composition of the phase-change recording material comprise Sb, Te, Ge, Ag, and In in the respective range of atomic ratio of:
  • the second object of the present invention can be achieved by the same phase-change recording material as described above.
  • the third object of the present invention can be achieved by a method of producing the above-mentioned optical recording medium, comprising the step of forming the recording layer by performing sputtering, using a target, with a sputtering power of 0.1 kW to 1.5 kW, the target being prepared by fusing and mixing a composition composed of a plurality of elements with a predetermined composition, crushing the composition to prepare a pulverized composition, and sintering said pulverized composition.
  • the third object of the present invention can also be achieved by a method of producing the above-mentioned optical recording medium, comprising the step of forming the recording layer by performing sputtering, using the same target as mentioned above, with a sputtering pressure of 0.8 mTorr to 9 mTorr.
  • the third object of the present invention can also be achieved by a method of producing the above-mentioned optical recording medium, comprising the step of forming the recording layer by performing sputtering, using the same target as mentioned above, in a sputtering chamber with the pressure in the sputtering chamber being set at a vacuum degree of 9 ⁇ 10 ⁇ 7 Torr or less immediately before the recording layer is formed.
  • the fourth object of the present invention can be achieved by a method of writing information, reading written information, and rewriting written information in the above-mentioned optical recording medium with irradiating the optical recording medium with a laser beam with a spot diameter of 0.05 ⁇ to 2.0 ⁇ m.
  • the fourth object of the present invention can also be achieved by a method of writing information, reading written information, and rewriting written information in the above-mentioned optical recording medium with irradiating the optical recording medium with a linear recording speed of 1.2 m/s to 25 m/s, preferably with a linear recordinq speed of 3. 5 m/s to 18 m/s.
  • FIG. 1 is a diagram showing the relationship between the atomic ratio of Sb/(Sb+Te) and the recording linear velocity and preservation stability.
  • FIG. 2 is a diagram showing the relationship between the number of readings and the light intensity for reading and reading jitter characteristics.
  • FIG. 3 shows the results of an analysis by XRD or the crystal structure of each of recording materials at the initial crystallization thereof, which is used in the recording layer of the optical recording medium of the present invention.
  • FIGS. 4A and 4B are comparative diagrams indicating that the addition of Ge to the recording material significantly improves the preservation stability of the optical recording medium.
  • FIGS. 5 to 8 are graphs indicating the bonding state of the recording materials comprising Sb and Te when additional elements are added thereto, analyzed by an XAFS analysis, using synchrotron radiation.
  • FIG. 9 is a graph showing the relationship between the number of readings and the jitter characteristics of all optical recording disk in Example 1.
  • FIG. 10 is a graph showing the relationship between the number of readings and the jitter characteristics of an optical recording disk in Example 2.
  • FIG. 11 is a graph showing the relationship between the number of readings and the jitter characteristics of an optical recording disk in Example 3.
  • FIG. 12 is a graph showing the relationship between the number of readings and the jitter characteristics of an optical recording disk in Example 4.
  • FIG. 13 is a graph showing the relationship between the number of readings and the jitter characteristics of an optical recording disk in Example 5.
  • FIG. 14 is a graph showing the relationship between the number of readings and the jitter characteristics of an optical recording disk in Comparative Example 1.
  • FIG. 15 is a graph showing the relationship between the number of readings and the jitter characteristics of an optical recording disk in Comparative Example 2.
  • the optical recording medium of the present invention comprises a recording layer comprising a phase change recording material which is capable of performing a reversible phase change from a crystalline phase to an amorphous phase and vice versa by light irradiation of the phase-change recording material,
  • the recording layer being capable of writing information therein, reading written information therefrom, and rewriting written information by utilizing the reversible phase change of the phase-change recording material
  • the term “jitter” is defined by a value of ⁇ /Tw, wherein ⁇ is a standard deviation of the leading and trailing edges of a recording mark with reference to clock signals, and Tw is a detection window width of the clock signals.
  • FIG. 2 shows the relationship between the reading light intensity and reading jitter characteristics and the number of readings.
  • ⁇ r denotes the reading jitter from the 2nd reading on.
  • the continuous wave laser beam having such an intensity Pr that satisfies the condition of 1.1 ⁇ R ⁇ 2.0, wherein R ⁇ repeat / ⁇ 1 , has an intensity which is about 1.1 to 2 times greater than that of a continuous wave laser beam used in the conventional drives.
  • the use of this continuous wave laser beam is intended to subject the recording mark to forced and accelerated deterioration.
  • the irradiation is carried out with a power of 0.3 mW to 0.8 mW, while in the measurement for the present invention, the irradiation is carried out with a power of 0.7 mW to 1.5 mW.
  • the recording mark is formed with a conventional recording power of about 6 mW to 20 mW.
  • the recording linear velocity is in the range of about 3.5 m/s to about 8.5 m/s.
  • the light spot diameter is about 0.8 ⁇ m to 1.0 ⁇ m.
  • optical recordirng media in which d ow >d 1 , have the shortcoming that when the recording linear velocity is increased, the preservation stability and the reading optical stability deteriorate, and in contrast to this, when the optical recording media in which a recording material with d ow ⁇ d 1 is used exhibit excellent correspondence to recording linear velocity, reading optical stability and preservation stability.
  • the optical recording medium of the present invention satisfies the relationship of d 1 >d ow , in which d 1 is the jitter increasing ratio of an initial writing mark, and d ow is a jitter increasing ratio at a 1000-times rewritten recording mark, when reading is performed under the above-mentioned conditions.
  • the optical recording medium which satisfies the above-mentioned conditions has excellent correspondence to recording linear velocity, reading optical stability and preservation stability and can be sufficiently used for DVD-RW.
  • the recording layer of the optical recording medium of the present invention comprises a phase-change recording material which in capable of performing a reversible phase change from a crystalline phase to an amorphous phase and vice versa by light irradiation of the phase-change recording material.
  • the phase-change recording material may comprise a pseudo binary composition, which has an NaCl-type crystal structure in the crystalline phase, wherein the pseudo binary composition is represented by Sb-TeM, comprising two portions, one portion being represented by Sb, and the other portion being represented by TeM, in which M represents a metal compound comprising at least Sb or Ge, provided that when TeM is Sb 2 Te 3 , the pseudo binary composition is a pseudo binary eutectic composition, and that at least one of the portions represented by TeM comprises Sb, and at least one of the other portions represented by TeM comprises Ge.
  • the pseudo binary composition is represented by Sb-TeM, comprising two portions, one portion being represented by Sb, and the other portion being represented by TeM, in which M represents a metal compound comprising at least Sb or Ge, provided that when TeM is Sb 2 Te 3 , the pseudo binary composition is a pseudo binary eutectic composition, and that at least one of the portions represented by TeM comprises Sb, and at least one of the other
  • the above-mentioned pseudo binary composition and the NaCl-type crystal structure in the crystalline phase can be identified by an XRD (X-ray diffraction) analysis and an XAFS (Extended X-ray Absorption Fino Structure) analysis.
  • FIG. 3 shows the data of the crystalline structures of recording materials, SbTe, AgInSbTe, and AgGeInSbTe, at the initial crystallization thereof for use in the recording layer of the optical recording medium of the present invention, obtained by XRD.
  • the total content ratio A of Sb and Te in terms of atomic ratio contained in the pseudo binary composition of the phase-change recording material be in a range of 0.80 ⁇ A ⁇ 0.97 from the viewpoints of the recording linear velocity and the reading optical stability.
  • the contents of Sb and Te in terms of atomic ratio contained in the pseudo binary eutectic composition of the phase-change recording material satisfy a relationship of 0.65 ⁇ Sb/(Sb+Te) ⁇ 0.85 from the same viewpoints as mentioned above.
  • the tendency shown in FIG. 1 is considered to support this.
  • the content ratio B of Ge in terms of atomic ratio contained in the pseudo binary composition of the phase-change recording material be in a range of 0.01 ⁇ B ⁇ 0.07, more preferably 0.01 ⁇ R ⁇ 0.05.
  • the thus added Ge serves to hinder the reduction of the preservation stability when the correspondence to the recording linear velocity is further improved in the above-mentioned relationship of the composition of Sb and Te.
  • FIG. 4A drd FIG. 4B respectively compare the jitter characteristics when Ge was not added, and the jitter characteristics when Ge was added, namely FIG. 4A is for Ag 2.5 In 3.0 xSb 71.5 Te 23.07 , and FIG. 4B is for Ag 0.5 In 3.0 Sb 71.5 Te 23.0 Ge 2.0 .
  • two sample optical recording media were fabricated by sputtering on a disk-shaped substrate made of polycarbonate with a diameter of 120 mm and a thickness of 0.6 mm the following layered structure composed of (a) an undercoat layer composed of Zn ⁇ SiO 2 with a thickness of 100 nm, (b) a recording layer composed of any of the above-mentioned recording materials (Ag 2.5 In 3.0 xSb 7.15 Te 23.0 or Ag 0.5 In 3.0 Sb 71.5 Te 23.0 Ge 2.0 ) with a thickness of 20 nm formed on the first protective layer, (c) a protective layer composed of Zn ⁇ SiO 2 with a thickness of 20 nm formed on the recording layer, and (d) a reflection layer made of Al with a thickness of 140 nm formed on the protective layer.
  • a recording layer composed of any of the above-mentioned recording materials (Ag 2.5 In 3.0 xSb 7.15 Te 23.0 or Ag 0.5 In 3.0 Sb 71.5 Te 23
  • FIG. 4A and FIG. 4B The results of the measurement of the jitter characteristics are shown in FIG. 4A and FIG. 4B.
  • the numbor for each curve denotes the number of rewriting, provided that the number 1 indicates writing of the recording mark one time.
  • a recording material comprising Sb, Te and Ge for use in the recording layer have the following composition of Sb, Te and Ge in terms of atomic ratio thereof;
  • Sb 0.60 to 0.80, more preferably 0.63 to 0.75,
  • Te 0.15 to 0.30, more preferably 0.20 to 0.25,
  • Ge 0.01 to 0.07, more preferably 0.02 to 0.05.
  • the pseudo binary composition of the phase-change recording material may further comprise as an additional element at least one element selected from the group consisting of Ag, In and Bi, in order to improve the characteristics of the optical recording medium such as the modulation degree of the recording marks.
  • the atomic ratio thereof be in the range of about 0.01 to 0.09.
  • FIGS. 5 to 8 show the results of the analysis of recording materials including the above-mentioned additional elements with respect to the bonding state thereof by an Sb-K-Edge XAFS analysis using synchrotron radiation.
  • the results of the analysis indicate that the additional elements are bonded to Te.
  • the pseudo binary composition of the phase-change recording material comprise Sb, Te, Ge, Ag, and in in the respective ranges of atomic ratio of;
  • Sb 0.60 to 0.80, more preferably 0.63 to 0.75,
  • Te 0.15 to 0.30, more preterably 0.20 to 0.25,
  • Ge 0.01 to 0.07, more preferably 0.02 to 0.05,
  • Ag 0.001 to 0.03, more preferably 0.001 to 0.02, and
  • optical recording media usinq the phase-change recording material with the above-mentioned compositions exhibit extremely excellent C/N ratio, erasing ratio, sensitivity, jitter characteristics, correspondence to recording linear velocity, reading optical stability, and preservation stability, and accordingly can be sufficiently used in DVD-RW.
  • the recording layer of the optical recording medium of the present invention can be formed by a conventional film formation method such as sputtering.
  • the sputtering was conducted by DC magnetron sputtering under the conditions that the applied power was 0.5 kW, the pressure of Ar gas was 2 mTorr, and the back pressure in a film formation chamber immediately before the formation of the recording layer was 1 ⁇ 10 7 Torr.
  • the sputtering rate for the formation of the recording layer was 1.2 times or more than the sputtering rate in the Rf sputtering which was adopted previously.
  • the DC magnetron sputtering is capable of forming the recording layer in a shorter time.
  • the DC magnetron sputtering is capable of forming the recording layer comprising the recording material with the above-mentioned crystal structure, compositions and characteristics.
  • the recording layer have a thickness of 5 nm to 30 nm, more preferably a thickness of 10 nm to 20 nm.
  • the optical recording medium of the present invention comprises the above-mentioned recording layer which is provided on a substrate.
  • the materials for the substrate glass, ceramics, and resins can be employed.
  • resins are preferable for forming the substrate. This is because a resin substrate is advantageous over other substrates in terms of fabrication and cost.
  • Representative examples of the resin for forming the substrate are polycarbonate resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, and polymethyl methacrylate resin.
  • polycarbonate resin is the most preferable of the above-mentioned resins.
  • the substrate can be variously shaped, for example, disk shaped, card shaped, or sheet-shaped, with an arbitrary thickness, such as 1.2 mm, 0.6 mm, and 0.3 mm.
  • an ultraviolet absorbing layer be provided on at least one side of the optical recording medium.
  • oxides such as SiO, SiO 2 ZnO, SnO 2 , Al 2 O 3 , TiO 2 , In 2 O 3 , MgO and ZrO 2 l nitrides such as Si 3 N 4 , AlN, TiN, BN and ZrN, sulfides such as ZnS, In 2 S 3 and TaS 4 , carbides such as SiC, TaC, B 4 C, WC, TiC And ZrC, diamond-like carbon, and mixtures thereof.
  • oxides such as SiO, SiO 2 ZnO, SnO 2 , Al 2 O 3 , TiO 2 , In 2 O 3 , MgO and ZrO 2 l nitrides such as Si 3 N 4 , AlN, TiN, BN and ZrN, sulfides such as ZnS, In 2 S 3 and TaS 4 , carbides such as SiC, TaC, B 4 C, WC, TiC And ZrC, diamond-like carbon, and
  • the undercoat layer and the protective layer can be formed, for instance, by sputtering, ion plating, vacuum deposition, and plazma CVD.
  • the undercoat layer have a thickness of 20 nm to 250 nm, more preferably 40 nm to 250 nm, furthermore preferably 160 nm to 250 nm.
  • the protective layer have a thickness of 5 nm to 150 nm, more preferably 10 nm to 30 nm.
  • the materials for the reflection layer there can be employed metal materials such as Al, Ag and Au, and the metal materials to which additive materials such as Ti, Cr, and Si are added.
  • the reflection layer can be formed, for instance, by sputtering, ion-plating, vacuum deposition, and plasma CVD.
  • the reflection layer have a thickness of 50 nm to 200 nm, more preferably 80 nm to 150 nm.
  • the materials for the hard coat layer be ultraviolet curing resins such as urethane acrylate, acrylate, and mixtures thereof, although the materials therefor are not limited to such ultraviolet curing resins.
  • the hard coat layer have a thickness of about 1 ⁇ m to about 50 ⁇ m.
  • the spot diametor of the beams be in the range of 0.05 ⁇ m to 2 ⁇ m, more preferably in the range of 0.1 ⁇ m to 1.6 ⁇ m.
  • the power of the writing light be about 8 mW to about 20 mW, and the power of the reading light be about 0.3 mW to about 1.0 mW.
  • the writing light and the reading light have a wavelength of 200 nm to 1000 nm, more preferably a wavelength of 400 nm to 800 nm.
  • the recording linear velocity be in the range of 1 m/s to 30 m/s, more preferably in the range of 1.2 m/s to 18 m/s.
  • a recording layer was formed by use of a target with the composition of Sb 74.0 Te 21.0 Ge 5.0 as shown in TABLE 1 by DC magnatron sputtering under the following conditions; Back pressure: 1 ⁇ 10 ⁇ 7 Torr Gas used: Ar Applied power: 0.5 kW Gas pressure: 2 mTorr
  • Example 1 The procedure of the fabrication of the optical recording disk No. 1 of the present invention in Example 1 was repeated in the same manner as in Example 1 except that the target used in Example 1 was replaced by the respective targets with the compositions as shown in TABLE 1, whereby optical recording disks No. 2 to No. 5 of the present invention, and comparative optical recording disks No. 1 and No. 2 were fabricated.
  • Each optical recording disk with a recording mark recorded therein was preserved at a temperature as high as 80° C. to 90° C. and a humidity as high as 85% RH, and the recording characteristics (jitter characteristics) were compared before and after the preservation.
  • Each optical recording disk was continuously irradiated with a reading light beam with a power of about 0.5 mw to about 1.5 mW, and the chances in the jitter characteristics in the reading were monitored.
  • the optical recording disks of the present invention have excellent preservation stability and reading optical stability. Furthermore, the optical recording disks of the present invention had a correspondence to recording linear velocity of 8 m/s to 13.5 m/s, which was excellent. This corresponds to 2 to 3 times the recording linear velocity of DVD-ROM in the same recording density as that of DVD-ROM.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Thermal Transfer Or Thermal Recording In General (AREA)
  • Optical Record Carriers And Manufacture Thereof (AREA)
  • Optical Recording Or Reproduction (AREA)
  • Manufacturing Optical Record Carriers (AREA)
US09/821,204 2000-03-31 2001-03-29 Optical recording medium, recording material, method of producing optical recording medium, and optical recording, reading and rewriting method Abandoned US20010041240A1 (en)

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US10/976,061 US20050058055A1 (en) 2000-03-31 2004-10-27 Optical recording medium, recording material, method of producing optical recording medium, and optical recording, reading and rewriting method
US11/410,791 US7364781B2 (en) 2000-03-31 2006-04-24 Optical recording medium, recording material, method of producing optical recording medium and optical recording, reading and rewriting method

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US20060188686A1 (en) 2006-08-24
US20050058055A1 (en) 2005-03-17
US6884487B2 (en) 2005-04-26
US7364781B2 (en) 2008-04-29
JP4112153B2 (ja) 2008-07-02

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