JP2003223723A - Disk optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent recorded data from being taken into a computer by disabling the reading in the high-speed reproduction, and to protect the copyright. <P>SOLUTION: The films of transparent dielectric film 11 (Si<SB>3</SB>N<SB>4</SB>, the thickness of equal to 10 nm)/phase change film 12 (Ge<SB>2</SB>Sb<SB>2</SB>Te<SB>5</SB>, 10 nm)/transparent dielectric film 13 (Si<SB>3</SB>N<SB>4</SB>, 130 nm)/metal reflective film 2' (Ag, 60 nm) are deposited on a substrate 1. The film 12 is not deposited on the inner circumferential side, and the metal reflective film 2' is exposed. The film 12 as deposited is in an amorphous state, and is changed from the amorphous state to a crystalline state by an initialization process. The reflectance of the film 12 in the crystalline state is lower than that in the amorphous state. In the reproduction at one-fold velocity, the amorphous phase is generated by the thermal energy of a laser beam to increase the reflectance, and the reproduction can be performed. In the CD-ROM device, the amorphous phase is not generated due to the high-speed rotation, and the reflectance remains low. Therefore, the reproduction cannot be performed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc-shaped recording medium applied to a read-only (ROM) type optical disc.

[0002]

2. Description of the Related Art The standard for a compact disc (CD), which is widely used today, is called compact disc audio (CD-DA), and is a standard document (Red Book).
It is based on the standard described in. On the basis of this standard, various formats including a CD-ROM have been standardized to form a so-called CD family. In the following description, when simply referred to as CD, CD
Read-only discs of various formats included in the family are collectively referred to.

Since the CD does not employ a special copy protection technique, there has been a problem that recorded music data is easily digitally copied. Especially recently
BACKGROUND ART CDs are played back by a CD-ROM drive of a personal computer, music data is loaded into a hard disk of the personal computer, and the loaded music data is processed or copied to a CD-R (Recordable).

[0004]

As described above, the fact that music information that is not missing from a CD can be taken out as digital data in this way provides convenience, but it causes a problem of copyright protection, which is a major social problem. . Original C
The copyright is infringed by transferring or selling the CD-R having the same content as that of D to another person. In particular, recently, music information copied via a network using a file exchange system or the like has been widely distributed, and the problem of copyright protection has become more serious.

On the other hand, CDs and CD players are already widely used, and it is virtually impossible to change the format and the like. Further, since the CD format is standardized in detail so that the player can reproduce the CD without any problem in all the formats, it is drastic that the digital signal carries additional information to prevent copy. The reality is that no solution can be expected.

Therefore, an object of the present invention is to provide a disc-shaped optical recording medium capable of preventing copying with almost no modification to the existing standard.

[0007]

In order to solve the above-mentioned problems, according to the invention of claim 1, in a read-only disk-shaped optical recording medium, a temperature is applied to a disk substrate having a pit row containing recording information. When a thin film whose reflectance increases due to temperature rise is deposited and reproduction is performed at a first linear velocity that is close to the standard linear velocity of the medium, the reflectance increases due to temperature increase, and the reading of the pit train is not possible. Is possible,
At the second linear velocity, which is higher than the first linear velocity, the disc-shaped optical recording medium cannot read the pit train.

The present invention focuses on the fact that the drive for computer use rotates and reproduces the optical disk at a rotational speed several times higher than that of the audio player.
It makes the reproduction of the optical disk impossible and prevents the data of the optical disk from being taken into the hard disk of the computer. In this way, by preventing the music information included in the optical disc from being taken into the computer, it is possible to prevent the data from being copied to another recordable disc via the computer or being transmitted / received on the network. be able to. When the optical disk is rotated at a speed close to the specified speed, it can be reproduced by an existing audio player. By making high-speed reproduction impossible, it is possible to prevent illegal copying of data from an optical disk via a computer or exchange of data via a network, so that copyright protection can be effectively achieved.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to a CD will be described below. For reference in understanding the present invention, the existing CD will be described.

FIG. 1 is an enlarged view of a part of a CD. Predetermined track pitch Tp (eg, 1.6 μm)
On the track, concave portions called pits and lands where pits are not formed are alternately formed. The length of the pit and the land is within the range of 3T to 11T. T is the shortest inversion interval. The CD is irradiated with laser light (having a wavelength of 780 nm, for example) from below.

The thickness of 1.
It has a structure in which a transparent disk substrate 1 of 2 mm, a reflective film 2 coated thereon, and a protective film 3 coated on the reflective film 2 are sequentially laminated. The reflection film 2 is a metal reflection film having a high reflectance, such as aluminum. In this invention, as will be described later, a thin film whose reflectance changes with temperature changes is applied to the disk substrate 1.

2A and 2B show the shape and mechanical dimensions of the CD. The dimensions in FIG. 2 are as follows.

A (diameter of the center hole 21) = 15 mm,
b = 26 mm, c = 33 mm, clamping area 22 = b
-C, d = 46mm, e = 50mm, lead-in area 23
= Ed, f = 116 mm, program area 24 = 33
mm, g = 117 mm, lead-out area 25 = g-f,
h (disc diameter) = 120 mm

FIG. 3 shows the flow of the existing CD manufacturing process. In step S1, a glass master having a photoresist, which is a photosensitive material, applied to a glass plate is rotated by a spindle motor, and the photoresist film is irradiated with laser light that is turned on / off according to a recording signal to create a master. It The photoresist film is developed, and in the case of a positive type resist, the exposed portion is melted and an uneven pattern is formed on the photoresist film.

One metal master is prepared by electroforming the photoresist master plate by plating (step S2). A plurality of mothers are created from the metal master (step S3), and further a plurality of stampers are created from this mother (step S4). A disk substrate is created using the stamper. Compression molding, injection molding, photo-curing, and the like are known as methods for producing a disk substrate. Then, in step S6, a reflective film and a protective film are deposited. In the conventional disc manufacturing method, a CD is further manufactured by performing label printing. In this invention, as will be described later, in step S6, a thin film whose reflectance changes due to temperature change is formed.

FIG. 4 shows a sectional structure of a disk according to an embodiment of the present invention. The first transparent dielectric film 1 is provided between the transparent disk substrate 1 having a thickness of 1.2 mm and the metal reflection film 2 '.
The laminated thin films are arranged so that the phase change film 12 is sandwiched between the first and second transparent dielectric films 13. The disc substrate 1 is produced through the mastering process and the stamping process as described above. A cover made of UV curable resin is attached to the metal reflection film 2 '.

More specifically, for the disc substrate 1,
The first transparent dielectric film 11 (Si₃N_Four, Film thickness = 10n
m) / phase change film 12 (Ge ₂Sb₂Te_Five, Film thickness = 10n
m) / second transparent dielectric film 13 (Si₃N_Four, Film thickness = 13
0 nm) / metal reflective film 2 '(Ag, film thickness = 60 nm)
A film is deposited.

These thin films 11, 12, 13, 2'are
In the step of depositing the reflective film and the protective film during the CD process (step S6 in FIG. 3), they are all sequentially formed by the magnetron sputtering method. The Si ₃ N ₄ (silicon nitride) films 11 and 13 were reactively sputtered with an Ar + N ₂ mixed gas and sputtered using an RF power supply. Also, GeSbTe having an atomic composition of 2: 2: 5.
(Germanium antimony tellurium) film 12 and A
The g thin film 2'uses Ar gas as a sputtering gas and
Sputtered with a C power supply.

When the GeSbTe film 12 is formed,
The area of 55mm in diameter is masked with a cover, and on the inner circumference side,
The GeSbTe film 12 is not formed and the metal reflective film 2 ′ is exposed. In this case, in the vicinity of the boundary of the diameter of 55 mm, due to the screening effect of the mask, GeSbTe
The film is formed so that the film thickness of the film 12 gradually becomes 10 nm. As explained with reference to FIG. 2, in this area,
The lead-in area 23 and the first part of the program area 24 are included.

In the lead-in area, TOC (Table Of
Management information called Contents) is recorded. TO
In C, the absolute time when each movement starts, the first movement number,
The last movement number and the absolute time when the lead-out starts are recorded. Normally, when reproducing a CD, the TOC in the lead-out area is first read into the reproducing device (CD-ROM drive). If you can't read the TOC,
It is judged as a disc error and the CD cannot be played back, or it cannot be recognized that the disc type is CD.
It is preferable that the TOC can be surely reproduced in order to avoid the problem that the reproduction is impossible or the disc type cannot be determined.

The CD-R / RW drive is a CD-
Discs such as DA, CD-ROM, and CD-R can be reproduced, the type of inserted disc is discriminated, and the recording / reproducing operation is optimized based on the discrimination result. Therefore, in the case of a disc having a low reflectance, there is a possibility that the drive discriminates the inserted disc as a CD-RW and makes such a disc reproducible. This means that
Even in the case of D and CD-ROM, it is inconvenient to reduce the reflectance and make reading impossible, and it is necessary for the drive to reliably discriminate the type of the disc. For the above-mentioned reason, the GeSbTe film is prevented from being formed in the inner peripheral area of the disk.

GeSbTe film 12 as a phase change material
Is in an amorphous state immediately after film formation. Initialization processing is performed on the optical disc on which such a thin film is formed. That is, the GeSbTe film 12 is changed from the amorphous state to the crystalline state over the entire surface by rotating at a standard linear velocity of 1.4 m / s and scanning with a laser beam having a light intensity of 20 mW at a wavelength of 780 nm. In the thin film structure shown in FIG. 4, the reflectance of the GeSbTe film 12 in the crystalline state is lower than that in the amorphous state.

In a normal phase-change type disk, the reflectance in a recording mark (amorphous) is low and is recognized as a mark, but in one embodiment, the reflectance in the amorphous state is higher than that in the crystalline state. It is considered expensive. Depending on the structure of the thin film such as the film thickness, the reflectivity can be changed in this way opposite to that of the normal phase change type disk. In a normal phase change type disk, the reflectance is (crystal state: 20%, amorphous state: 0%). In one embodiment, the reflectance is optimized so as to exceed the CD standard of 65%, and the reflectance is, for example, (crystalline state: 30-40%, amorphous state: 75%).

Since the disc thus produced is not sufficiently optimized with respect to the intensity of the reproducing light, the CD connected to the audio CD player and the computer is not optimized.
An experiment was conducted by modifying the laser light intensity of the ROM drive to 7 mW. As a result, audio CD
When I played it back on the player, I could play all songs without any problems. On the other hand, when this disc was inserted into the CD-ROM drive (up to 32x speed), the song was displayed.
When it was played with the CD playback software attached to ndows (registered trademark) 98, the playback stopped in a few minutes and could not be played.
Further, when an attempt was made to convert the contents of the CD into the WAV format using the CD-R copy software, a normal file could not be obtained. Ie CD
-R could not be copied.

Now, in order to measure the film thickness dependence of the reflectance of the disc in one embodiment, a similar multilayer film was formed on a separate glass plate and the reflectance was measured. The result is shown in FIG. In FIG. 5, 31 indicates the change in the reflectance of the GeSbTe film 12 in the amorphous state (the central portion of the light spot during low linear velocity reproduction), and 32 indicates the GeSbTe film 12
Shows the change in reflectance in the crystalline state (at the center of the light spot during room temperature and high-speed reproduction). In the area on the disk inner peripheral side where the film thickness of the GeSbTe film 12 is 0, the reflectance is high and C
It satisfies the D standard and is reproducible.

When the GeSbTe film 12 is in an amorphous state, the CD having a reflectance of 65% or more is obtained regardless of the film thickness.
It is reproducible by entering the standard of. On the other hand, if the GeSbTe film 12 is in a crystalline state, the film thickness is 5 nm or more and the reflectance is 50% or less, which is outside the range of the CD standard and cannot be reproduced.

A case where a disc according to an embodiment of the present invention is reproduced by an audio CD player and a CD-ROM drive connected to a computer will be described. The reproducing light intensity is 7 mW on both sides. In the case of an audio CD player, the linear velocity during reproduction is 1.2 m / s to 1.4 m / s. At this linear velocity, the temperature at the center of the light spot rises and the GeSbTe film 12 becomes amorphous. As a result, the reflectance increases and exceeds 65%, and the pits can be read and the information can be reproduced. That is, the reflectance of only the spot portion being reproduced becomes high, and the other portion is gradually cooled after being scanned and returns to the crystalline state.

On the other hand, the CD-ROM drive has a maximum of 3
It's 2x speed and at least 4x speed,
Since the linear velocity is 5 m / s to 40 m / s, the temperature rise is extremely low. The faster the linear velocity, the shorter the time it takes to pass a point on the disc and the less thermal energy is applied. Therefore, it is conceivable that the recorded information cannot be read because the GeSbTe film 12 does not become amorphous and the reflectance remains low even in the central portion of the spot.

Since no GeSbTe film is formed at the beginning of the lead-out area 23 and the program area 24, the audio CD player and the CD-R are not formed.
Any of the OM drives can read the TOC and prevent the disc error from being determined. CD-R /
In the case of the RW drive, the disc type can be surely determined. In addition, the GeSbTe film is gradually regulated in thickness (see FIG.
Since the film is formed so as to have a thickness of 10 nm), as the light spot changes the scan position to the outer peripheral side, Ge
It gradually enters the area where the SbTe film is formed. CD-R
In the case of the OM drive, the reflectance gradually decreases, and when it enters the area where the film thickness is 2 to 3 nm, the reflectance falls below 65% to the CD standard limit. Furthermore, the film thickness is 5n
In the area of m or more, the reading cannot be performed completely and the reproduction cannot be performed. On the other hand, in an audio CD player that reproduces at a standard linear velocity, the reflectivity is 65% or more regardless of the film thickness because the GeSbTe film becomes amorphous at the center of the spot of the laser beam during reproduction. Is reproducible.

In one embodiment, as shown in FIG.
Although the thickness of the SbTe film 12 is set to 10 nm, an experiment was conducted with this set to 5 nm. As a result, audio C
Playback was possible with the D player, but not with the CD-ROM drive. From the results shown in FIG. 5, if the film thickness is in the range of 5 nm or more, it is possible to reproduce at low linear velocity and not to reproduce at high linear velocity.

Next, another embodiment of the present invention will be described. In another embodiment, silicon naphthalocyanine [Silicon 2,3-naphtalocyanine b
is (trihexylsililoxide)] is used. Since this material is a saturable absorption dye and has a material whose optical constant changes at a lower temperature than GeSbTe, laser light of lower intensity can be used as the reproduction laser light. For example, 2 on the board
By using the reproducing laser beam having the intensity of mW, it was possible to reproduce at a low linear velocity and not to reproduce at a high linear velocity, as in the one embodiment. The intensity of the laser light of the audio CD player of the actual product is around 1 mW, and in another embodiment, by slightly optimizing the sensitivity,
It can be applied to an already commercialized audio CD player.

The present invention is not limited to the above-described embodiments of the present invention and the like, and various modifications and applications are possible without departing from the gist of the present invention. For example, in one embodiment using a phase change material, the Si ₃ N ₄ film thickness can be other than the values shown in FIG. The film structure is not limited to that shown in FIG. 4, and various modifications are possible. G as a phase change material
Other than eSbTe can be used, and the material of the reflective film is Ag.
Other than can be used. Further, various modes are possible as a mode of depositing the thin film having a variable reflectance. The method is not limited to the method of completely depositing the film whose reflectance changes, but the film thickness may be changed so that the film is not substantially deposited. Furthermore, the present invention is not limited to CDs, but can be applied to other read-only optical discs such as single CDs.

[0033]

As is apparent from the above description, according to the present invention, it is possible to provide an optical disc which can be reproduced at a low linear velocity and cannot be read at a high linear velocity. Usually, the optical disk drive connected to the computer is
Since it is configured for high speed playback, the optical disc according to the present invention cannot be read by an optical disc drive. Therefore, it is possible to prevent the read digital data from being taken into the hard disk of the computer. As a result, it is possible to prevent the data from being copied to the writable disc by the computer and transmitted / received through the network, and it is possible to effectively protect the copyright of the data recorded on the disc. Also, although it is possible to read at 1x speed, it takes a lot of time to import the data, and it often feels guilty to copy, so copying at 1x speed is practically possible. Can be stopped.

Further, on the optical disc, in the area where the management information such as disc type identification information is recorded, the reflection film is exposed without forming a film whose optical characteristics change. As a result, it is possible to prevent the disc from being determined to be unreadable, and it is possible to reliably determine the type of the disc. Thereby, copyright protection can be ensured more reliably.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a conventional CD recording pattern and a CD structure.

FIG. 2 is a schematic diagram for explaining the shape and size of a conventional CD.

FIG. 3 is a schematic diagram for explaining a conventional CD manufacturing process.

FIG. 4 is a schematic diagram showing a film structure of an embodiment of the present invention.

FIG. 5 is a graph showing the film thickness dependence of reflectance in the film structure of one embodiment.

[Explanation of symbols]

1 ... Disk substrate, 2, 2 '... Metal reflective film, 1
1 ... First transparent dielectric film, 12 ... Phase change film, 1
3 ... second transparent dielectric film

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5D029 JA04 JB45 JC02                 5D090 AA01 BB02 BB11 BB20 CC04                       CC14 DD02 EE20

Claims (6)

[Claims] 1. A read-only disc-shaped optical recording medium, wherein a thin film whose reflectance increases with temperature rise is deposited on a disc substrate having a pit row containing recorded information, and the linear velocity of the standard of the medium is applied. When the reproduction is performed at a first linear velocity substantially close to the above, the reflectance is increased due to the temperature rise, and the pit row can be read out, and the second linear velocity faster than the first linear velocity is obtained. A disc-shaped optical recording medium in which reading of the pit train is impossible at speed. 2. The thin film according to claim 1, wherein the thin film is substantially partially deposited, and the partial area where the thin film is not deposited is an area in which management information is recorded. Disc-shaped optical recording medium. 3. The first thin film according to claim 1, wherein the thin film is applied to the disk substrate.
Transparent dielectric film, a phase change film adhered to the first transparent dielectric film, a second transparent dielectric film adhered to the phase change film, and a second transparent dielectric film 2. A disk-shaped optical recording medium, comprising: 4. The disk-shaped optical recording medium according to claim 1, wherein the thin film includes a phase change film, and the thin film has a higher reflectance in an amorphous state than in a crystalline state. 5. The disk-shaped optical recording medium according to claim 1, wherein a saturable absorbing dye is used as the thin film. 6. The reflectance according to claim 1, wherein the reflectance at room temperature is 50% or less at a wavelength of 770 nm to 870 nm, and the reflectance is 65% or more at the first linear velocity. Disc-shaped optical recording medium.