Magneto-optical disk having write-once identification marks and method for recording thereof

• US 6,266,299 B1
• Filed: 05/20/1999
• Issued: 07/24/2001
• Est. Priority Date: 12/19/1996
• Status: Expired due to Term

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Oshima, Mitsuaki, Gotoh, Yoshiho, Tanaka, Shin-ichi, Koishi, Kenji, Moriya, Mitsurou, Murakami, Motoyoshi, Takemura, Yoshinari, Miyatake, Norio, Konishi, Shinichi
• Primary Examiner(s): DINH, TAN X
• Application Number:
  US09/308,550
• Time in Patent Office: 796 Days
• Field of Search: 369/13, 369/14, 369/110, 369/116, 369/275.1, 300/59, 300/114, 365/122, 428/694.ML, 428/694.MM, 428/64.3
• US Class Current: 369/13.38
• CPC Class Codes: G06T 1/0021 Image watermarking
• CPC Class Codes: G06T 2201/0064 for copy protection or copy management, e.g. CGMS, copy only once, one-time copy
• CPC Class Codes: G11B 11/10506 by modulating only the light beam of the transducer
• CPC Class Codes: G11B 11/10515 Reproducing compensating pit shift G11B11/1053
• CPC Class Codes: G11B 11/10584 characterised by the form, e.g. comprising mechanical protection elements
• CPC Class Codes: G11B 11/10595 Control of operating function
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/00123 the record carrier being identified by recognising some of its unique characteristics, e.g. a unique defect pattern serving as a physical signature of the record carrier
• CPC Class Codes: G11B 20/00166 involving measures which result in a restriction to authorised contents recorded on or reproduced from a record carrier, e.g. music or software
• CPC Class Codes: G11B 20/00181 using a content identifier, e.g. an international standard recording code [ISRC] or a digital object identifier [DOI]
• CPC Class Codes: G11B 20/0021 involving encryption or decryption of contents recorded on or reproduced from a record carrier
• CPC Class Codes: G11B 20/00231 wherein the key is obtained from a local external medium, e.g. a card
• CPC Class Codes: G11B 20/0026 the key being stored as a barcode
• CPC Class Codes: G11B 20/00268 said barcode being recorded in a burst cutting area [BCA]
• CPC Class Codes: G11B 20/00347 wherein the medium identifier is used as a key
• CPC Class Codes: G11B 20/00876 wherein physical copy protection means are attached to the medium, e.g. holograms, sensors, or additional semiconductor circuitry
• CPC Class Codes: G11B 20/00884 involving a watermark, i.e. a barely perceptible transformation of the original data which can nevertheless be recognised by an algorithm
• CPC Class Codes: G11B 20/10 Digital recording or reproducing
• CPC Class Codes: G11B 20/1217 on discs
• CPC Class Codes: G11B 20/1258 where blocks are arranged within multiple radial zones, e.g. Zone Bit Recording or Constant Density Recording discs, MCAV discs, MCLV discs
• CPC Class Codes: G11B 2020/122 : Burst cutting area [BCA]
• CPC Class Codes: G11B 2020/1244 : CAV zone, in which a constant angular velocity is used
• CPC Class Codes: G11B 2020/1245 : CLV zone, in which a constant linear velocity is used
• CPC Class Codes: G11B 23/281 : by changing the physical properties of the record carrier
• CPC Class Codes: G11B 23/288 : Protecting disks from being written or overwritten
• CPC Class Codes: G11B 23/40 : Identifying or analogous means applied to or incorporated in the record carrier and not intended for visual display simultaneously with the playing-back of the record carrier, e.g. label, leader, photograph
• CPC Class Codes: G11B 7/0037 : with discs
• CPC Class Codes: G11B 7/0045 : Recording G11B7/006, G11B7/0065 take precedence
• CPC Class Codes: G11B 7/00736 : Auxiliary data, e.g. lead-in, lead-out, Power Calibration Area [PCA], Burst Cutting Area [BCA], control information sector headers or adresses in prepits G11B7/00745; address data in track wobble G11B7/24082
• CPC Class Codes: G11B 7/24 : Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the arrangement of information on the carrier G11B7/007

Abstract

An optical disk and a method for storing write-once information usable for preventing the illegal copies. The optical disk comprises a disk substrate, and a recording layer having a magnetic film disposed on the disk substrate. The optical disk stores write-once information formed by first recording areas and second recording areas and the write-once information being different for each disk. The second recording areas are formed as a plurality of stripe-shaped marks that are oblong in a radial direction of the disk by irradiating laser light based on a modulation signal of the write-once information in the pre-determined portion of the recording layer, in a manner that a magnetic anisotropy in a direction perpendicular to a surface of the second recording areas is smaller than a magnetic anisotropy in a direction perpendicular to a surface of the first recording areas.

Claims

1. An optical disk comprising:

a disk substrate; and

a recording layer on the disk substrate, the recording layer including a magnetic film with magnetic anisotropy in a direction perpendicular to a surface of the magnetic film;

wherein

the optical disk stores write-once information, the write-once information being unique for the disk, formed by first recording areas and second recording areas in a pre-determined portion of said recording layer;

a magnetic anisotropy in a direction perpendicular to a surface of the second recording areas is smaller than a magnetic anisotropy in a direction perpendicular to a surface of the first recording areas;

the second recording areas are formed as stripe-shaped marks that are oblong in a radial direction of the disk; and

a plurality of the stripe-shaped marks is arranged in a circumferential direction of the disk, the arrangement being based on a modulation signal of the write-once information.

2. The optical disk according to claim 1, further comprising an identifier for indication whether there is a row of a plurality of marks arranged in a circumferential direction of the disk.

3. The optical disk according to claim 2, wherein the identifier indicating the row of marks is stored among control data.

4. The optical disk according to claim 1, wherein the pre-determined portion comprising write-once information is at an inner perimeter portion of the disk.

5. The optical disk according to claim 1, wherein a difference between a luminous energy that is reflected from the first recording areas and a luminous energy that is reflected from the second recording areas is below a pre-determined value.

8. The optical disk according to claim 1, wherein the magnetic anisotropy of the magnetic film of the second recording areas in an in-plane direction is dominant.

9. The optical disk according to claim 1, wherein at least a portion of the magnetic film of the second recording areas is crystallized.

10. The optical disk according to claim 1, wherein said recording layer comprises a multilayer magnetic film.

6. A optical disk comprising:

a disk substrate; and

a recording layer on the disk substrate, the recording layer including a magnetic film with magnetic anisotropy in a direction perpendicular to a surface of the magnetic film;

wherein

the optical disk stores write-once information formed by first recording areas and second recording areas in a pre-determined portion of said recording layer;

a magnetic anisotropy in a direction perpendicular to a surface of the second recording areas is smaller than a magnetic anisotropy in a direction perpendicular to a surface of the first recording areas;

the second recording areas are formed as stripe-shaped marks that are oblong in a radial direction of the disk;

a plurality of the stripe-shaped marks is arranged in a circumferential direction of the disk, the arrangement being based on a modulation signal of the write-once information; and

wherein the difference between luminous energy that is reflected from the first recording areas and luminous energy that is reflected from the second recording areas is not more than 10%.

7. A optical disk comprising:

a disk substrate; and

a recording layer on the disk substrate, the recording layer including a magnetic film with magnetic anisotropy in a direction perpendicular to a surface of the magnetic film;

wherein

the optical disk stores write-once information formed by first recording areas and second recording areas in a pre-determined portion of said recording layer;

a magnetic anisotropy in a direction perpendicular to a surface of the second recording areas is smaller than a magnetic anisotropy in a direction perpendicular to a surface of the first recording areas;

the second recording areas are formed as stripe-shaped marks that are oblong in a radial direction of the disk;

a plurality of the stripe-shaped marks is arranged in a circumferential direction of the disk, the arrangement being based on a modulation signal of the write-once information; and

wherein a difference between an average refractive index of the first recording areas and an average refractive index of the second recording areas is not more than 5%.

11. (A method for recording write-once information onto an optical disk (a) comprising a disk substrate, and a recording layer on the disk substrate, including a magnetic film with a magnetic anisotropy in a direction perpendicular to a surface of the magnetic film;

and (b) storing write-once information formed by first recording areas and second recording areas in a pre-determined portion of said recording layer, the write-once information being unique for the disk;

the method comprising forming the second recording areas as a plurality of stripe-shaped marks that are oblong in a radial direction of the disk in a circumferential direction of the disk by irradiating laser light based on a modulation signal of the write-once information in a circumferential disk direction in the pre-determined portion of said recording layer, wherein a magnetic anisotropy in a direction perpendicular to a surface of the second recording areas becomes smaller than a magnetic anisotropy in a direction perpendicular to a surface of the first recording areas.

12. The recording method according to claim 11, wherein, when the second recording areas are formed, a laser light source is pulsed in accordance with a modulation signal of phase-encoded write-once information, and the optical disk is rotated.

13. The recording method according to claim 11, wherein the optical disk further comprises a reflective layer and a protective layer on the disk substrate, and an intensity of laser light irradiated to form the second recording areas is smaller than an intensity of laser light destroying at least one of the disk substrate, the reflective layer and the protective layer.

14. The recording method according to claim 11, wherein an intensity of laser light irradiated to form the second recording areas is an intensity for crystallizing at least a portion of said recording layer.

15. The recording method according to claim 11, wherein an intensity of laser light irradiated to form the second recording areas is larger than an intensity of laser light for heating said recording layer to a Curie temperature.

16. The recording method according to claim 11, wherein an intensity of laser light irradiated to form the second recording areas is an intensity for making a magnetic anisotropy of the magnetic layer of the first recording areas in an in-plane direction dominant.

17. The recording method according to claim 11, wherein, with a unidirectional convergence focusing lens, rectangularly stripe-shaped laser light is irradiated onto said recording layer when the second recording areas are formed.

18. The recording method according to claim 11, wherein a light source of the laser light that is irradiated for forming the second recording areas is a YAG laser.

19. The recording method according to claim 18, wherein a magnetic field above a pre-determined value is applied to said recording layer while irradiating laser light from the YAG laser.

20. The recording method according to claim 19, wherein the magnetic field applied to said recording layer is at least 5 kOe.