JPH10340486A - Optical disk, master disk manufacturing device of the same and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress fluidizing substance to move a phase transition recording layer in a land along the scanning direction of a light beam when the same part is repeatedly overwritten by providing a recess in about the middle of the surface of the land to be irradiated with the light beam. SOLUTION: At the time of recording the master disk of the optical disk in order to record the land/groove, a side lobe is formed at a prescribed distance from the center of a laser beam for cutting the master disk, and the cutting is performed by the laser beam set for an intensity ratio of center peak intensity P1 to side lobe peak intensity P2 of a laser spot in a range of 1/20 to 1/5 to manufacture the master disk having the recess in about the middle of the land along the track direction, and the optical disk is manufactured based on this master disk. By this method, fluidization of substance in the land can be suppressed, thus maintaining the satisfactory characteristic without deteriorating a byte error rate against the repetition of overwriting the land part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk for recording information by utilizing a reversible phase change between amorphous and crystalline under irradiation of a light beam, and a master for the optical disk. The present invention relates to an optical disc master manufacturing apparatus and an optical disc manufacturing method.

[0002]

2. Description of the Related Art In recent years, optical disks have attracted attention as large-capacity memories. Optical disks are roughly classified into three types: a read-only type represented by a CD, a one-time write once type represented by a CD-R, and a rewritable type represented by an external memory of a computer.

Further, the rewritable type is roughly classified into a magneto-optical disk and a phase change optical disk. A phase-change optical disc uses a phase-change recording layer that undergoes a reversible phase change between an amorphous phase and a crystalline phase when irradiated with a laser beam, and reflects a recording mark (amorphous) and a background crystalline state. It is responsible for recording and reproduction of information by utilizing the difference in rates. Whether the laser irradiated portion in the phase change recording layer becomes amorphous (recording mark) or crystalline (erased state) depends on whether the irradiated portion exceeds the melting point of the material constituting the phase change recording layer,
Or it only depends on whether it exceeds the crystallization temperature. Therefore, at the time of laser beam scanning, overwriting can be performed by modulating the intensity of the laser beam.

Here, a general layer structure of a phase change optical disk will be described with reference to FIG. As shown in FIG. 1, a phase-change optical disc 100 includes a transparent substrate 102 made of polycarbonate or glass and a first dielectric protection layer made of a ZnS / SiO ₂ mixed film in order from the surface opposite to the surface receiving the laser beam. Layer 104, a phase-change recording layer 1 made of, for example, a ternary alloy of Ge ₂ Sb ₂ Te _{5 that} changes reversibly between amorphous and crystalline by irradiation with a laser beam or the like.
06, a second dielectric protection layer 108 made of a ZnS / SiO ₂ mixed film, a metal reflection layer 110 made of an AlMo alloy, and a UV cured resin protection layer 112 for preventing scratches generated during handling of the disk. It has become.

The phase-change recording layer 106 is melted by irradiation with a laser beam, and becomes amorphous by being rapidly cooled. At this time, the first dielectric protection layer 104 and the second dielectric protection layer 108 Serves to prevent the phase change recording layer 106 from evaporating and making a hole, that is, a function of protecting the phase change recording layer from heat. Further, the first dielectric layer 104 is formed of the metal reflection layer 11.
It is designed for optical enhancement at the time of signal reproduction by a synergistic effect with 0, and its thickness is usually 500 to 300.
0 [angstrom] is set. The phase change recording layer 106 is usually designed to be very thin because it needs to be melted by irradiation with a laser beam, and is set to 50 to 300 [angstrom]. Second dielectric layer 10
8 is usually designed to be quite thin because it is necessary to release heat to the metal reflective layer 110 in order to quench the heat of the recording layer melted when irradiated with the laser beam as quickly as possible to make it amorphous. It is set to about 50 to 300 [angstrom]. The thickness of the metal reflective layer 110 is usually set to about 500 to 3000 [angstrom] for the purpose of enhancing the reproduction signal and escaping heat.

On the other hand, the biggest disadvantage of the phase change optical disk is that
This is deterioration of the phase change recording layer 106 when overwriting is repeated. When the phase-change optical disk is overwritten, it exceeds the melting point of the phase-change recording layer 106 and is rapidly cooled to form an amorphous phase.
When the overwriting of the same portion is repeated, the phase change recording layer 106 moves along the scanning direction of the laser beam because 6 melts. For example, as shown in FIG. 2, when the operation of irradiating a laser from point A, performing one rotation overwrite of the disk, and turning off the laser at point B is repeated by one track jump, the phase change recording layer 106 becomes As shown in the figure, the laser beam moves along the scanning direction of the laser beam (hereinafter, this will be referred to as a material flow). When the overwriting is repeated, the flow of the substance is accelerated, and the phase change recording layer 106 itself may be lost in some places, and data may be damaged.

As a material flow preventing measure for preventing such a material flow, as shown in FIG. 3, an adhesive layer (SiO ₂ ) for suppressing the flow and a phase change recording layer are provided above and below the phase change recording layer 106. Suppression layer 105 for reducing relative surface tension
And 107 are provided. In addition, as shown in FIG. 4, there is a method of mixing a material 114 having a high melting point that does not melt even when irradiated with a laser beam into the phase-change recording layer 106 to make it difficult to cause a substance flow.

[0008] The optical disk is provided with areas called lands and grooves, and tracks are formed by these lands and grooves. Material flow that can occur due to recording of information in the groove can be sufficiently prevented by the above-described material flow prevention measures. More specifically, even if overwriting is performed approximately 100,000 times by the above-described substance flow prevention measure, the level reaches a practically acceptable level. One of the reasons that the substance flow that can occur due to the recording of information in the groove is sufficiently prevented by the substance flow prevention measure is that the groove is unlikely to cause the substance flow. The reason why the substance does not easily flow in the groove is that there are walls on both sides of the groove G as shown in FIG. That is, the contact area between the phase change recording layer 106 and the substrate 102 is large. Thus, the problem of material flow in the groove has been effectively solved and the drive has been commercialized.

On the other hand, in recent years, land / groove recording (hereinafter referred to as L / G) for recording information on both lands and grooves of an optical disk has been proposed in order to improve the recording density of the optical disk.
G recording) has been proposed (previously, information was recorded only on one of the land and the groove). In this L / G recording, the mark recorded on the land is not visible when the laser beam is running on the groove, or the mark recorded on the groove is not visible when the laser beam is running on the land. Thus, the depth of the groove can be adjusted optically. According to this L / G recording, there is an advantage that the storage capacity can be doubled as compared with the method of recording information on either one of the groove and the land.

[0010]

However, in the case of the L / G recording, the material flow in the groove can be prevented by the above-mentioned material flow prevention measure, but there is a problem that there is no appropriate material flow prevention measure in the land. .

An object of the present invention has been made in view of the above circumstances, and provides an optical disk capable of suppressing a material flow in a land provided on the optical disk, an apparatus for manufacturing a master of the optical disk, and an optical disk manufacturing method. Is to do.

[0012]

Means for Solving the Problems To solve the above problems and achieve the object, an optical disk, an optical disk master manufacturing apparatus and an optical disk manufacturing method of the present invention are as follows. The present invention has concentric or spiral land and groove tracks, and at least uses the fact that a phase is reversibly changed into an amorphous state and a crystal state by irradiation with a light beam, and information is recorded at least on the land. In an optical disk for recording, the land has a recess along the track direction substantially at the center of the surface of the land receiving the light beam.

The present invention has concentric or spiral tracks of lands and grooves, and records information by utilizing the fact that it undergoes a reversible phase change between amorphous and crystalline when irradiated with a light beam. In an optical disk master manufacturing apparatus for manufacturing an optical disk master, the optical disk master having a recess along the track direction substantially at the center of the surface of the land that is irradiated with the light beam is manufactured.

The present invention has M concentric or spiral tracks of lands and grooves, and utilizes the fact that it undergoes a reversible phase change between amorphous and crystalline under irradiation of a light beam, thereby taking advantage of the information. In an optical disc master manufacturing apparatus for manufacturing a master of an optical disc for recording, an irradiation unit for irradiating a light beam for cutting the master, and a side for generating a predetermined side lobe in the light beam irradiated by the irradiation unit A lobe generating unit; and a control unit for controlling cutting of the master by a light beam having a predetermined side lobe generated by the side lobe generating unit.

The present invention has a concentric or spiral track of land and groove, and records information by utilizing a reversible phase change between an amorphous phase and a crystalline phase when irradiated with a light beam. In the optical disk manufacturing method for manufacturing an optical disk, the method includes manufacturing an optical disk having a depression along the track direction at substantially the center of the surface of the land receiving the light beam.

The present invention has a concentric or spiral track of land and groove, and records information by utilizing the fact that it undergoes a reversible phase change between an amorphous phase and a crystalline phase when irradiated with a light beam. An optical disk manufacturing method for manufacturing an optical disk, the method comprising: manufacturing an optical disk master having a recess along the track direction substantially at the center of a surface of the land receiving a light beam, and manufacturing an optical disk based on the manufactured master. I do.

The present invention has a concentric or spiral track of land and groove, and records information by utilizing the fact that it undergoes a reversible phase change between an amorphous phase and a crystalline phase when irradiated with a light beam. In an optical disk manufacturing method for manufacturing an optical disk, a light beam for cutting the master disk of the optical disk is irradiated, a predetermined side lobe is generated in the irradiated light beam, and a light beam having the predetermined side lobe is generated. The cutting of the master by the beam is controlled, and an optical disc is manufactured based on the master manufactured by the cutting under the control.

As a result of taking the above-described measures, the following operation occurs. (1) Since the optical disk of the present invention has a dent along the track direction substantially at the center of the surface of the land that is irradiated with the light beam, the phenomenon of material flow is suppressed by this dent, and overwriting is prevented. Can be strong.

(2) According to the optical disk master manufacturing apparatus of the present invention, an optical disk master having a depression along the track direction at substantially the center of the surface of the land that is irradiated with the light beam is manufactured. Therefore, an optical disk manufactured based on the master manufactured by the optical disk master manufacturing apparatus has a dent in the land, and the phenomenon of material flow is suppressed by the dent, thereby making it more resistant to overwriting.

(3) According to the optical disk manufacturing method of the present invention, an optical disk having a depression along the track direction at approximately the center of the surface of the land that is irradiated with the light beam is manufactured. Therefore, the optical disk manufactured by this optical disk manufacturing method has a dent in the land, and the phenomenon of material flow is suppressed by the dent, and the optical disk can be resistant to overwriting.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 shows a cutting apparatus (master manufacturing apparatus) for producing a stamper (master) serving as a mold for an optical disc (mastering step).

The cutting apparatus shown in FIG. 5 is a glass master 1 having no irregularities on which a photoresist is applied as a master of a phase change optical disk (DVD-RAM) for recording and reproduction.
Is rotated at a predetermined speed to irradiate the glass master 1 with a laser beam to melt the photoresist to form land tracks (recesses) and to form concave pits (recording marks). That is, the cutting device is turned on at a predetermined timing with respect to the glass master 1,
By irradiating the laser beam to be turned off, land tracks and pits are formed at predetermined positions of the glass master 1.

In FIG. 1, a glass master 1 coated with a photoresist is rotated by a motor 3 at a constant speed, for example. The motor 3 is controlled by a motor control circuit 4.

The cutting of the glass master 1 is performed by an optical head 5 as an irradiating means for irradiating the glass master 1 with a laser beam. The optical head 5 is fixed to a drive coil 7 constituting a movable portion of a linear motor 6, and the drive coil 7 is connected to a linear motor control circuit 8.

A speed detector 9 is connected to the linear motor control circuit 8, and a speed signal of the speed detector 9 is sent to the linear motor control circuit 8. Further, a permanent magnet (not shown) is provided at a fixed portion of the linear motor 6. When the drive coil 7 is excited by the linear motor control circuit 8, the optical head 5 moves in the radial direction of the glass master 1. It is supposed to be.

The optical head 5 holds an objective lens 10 by a wire or a leaf spring (not shown).
The objective lens 10 is moved in the focusing direction (the optical axis direction of the lens) by the drive coil 12 and is movable in the tracking direction (the direction orthogonal to the optical axis of the lens) by the drive coil 11.

A laser beam generated by a laser oscillator (for example, an argon neon laser oscillator) 19 driven by the laser control circuit 13 is supplied to a collimator lens 20, a half prism 21, an objective lens 10, and a ring 2.
00, the reflected light from the glass master 1 is reflected by the ring 200, the objective lens 10,
The light is guided to a photodetector 24 via a half prism 21, a condenser lens 22, and a cylindrical lens 23. The function of the ring 200 will be described later.

The photodetector 24 is a four-divided photodetector cell 24.
a, 24b, 24c and 24d.
The output signal of the photodetector cell 24a of the photodetector 24 is supplied to one end of adders 26a and 26d via the amplifier 25a, and the output signal of the photodetector cell 24b is supplied to the adders 26b and 26c via the amplifier 25b. The output signal supplied to one end and output from the photodetection cell 24c is supplied to the adder 2 via the amplifier 24c.
The output signals of the photodetection cells 24d supplied to the other ends of the photodetectors 6a and 26c are added to adders 26b and 26d via an amplifier 25d.
Is supplied to the other end.

The output signal of the adder 26a is a differential amplifier OP
2 and the non-inverting input terminal of the differential amplifier OP2 is supplied with the output signal of the adder 26b.
As a result, the differential amplifier OP2 includes the adders 26a, 26
A signal related to the focus point is supplied to the focusing control circuit 27 in accordance with the difference b. The output signal of the focusing control circuit 27 is supplied to the focusing drive coil 12, and the laser light is applied to the glass master 1
The above is controlled so that it is always in just focus.

The output signal of the adder 26d is a differential amplifier OP
1, and the output signal of the adder 26c is supplied to the non-inverting input terminal of the differential amplifier OP1.
As a result, the differential amplifier OP1 includes the adders 26d and 26d.
A track difference signal is supplied to the tracking control circuit 28 in accordance with the difference c. The tracking control circuit 28 creates a track drive signal according to the track difference signal supplied from the differential amplifier OP1.

The track drive signal output from the tracking control circuit 28 is applied to the drive coil 1 in the tracking direction.
1 is supplied. The track difference signal used in the tracking control circuit 28 is supplied to the linear motor control circuit 8.

The supply of the track drive signal to the drive coil 11 causes the objective lens 10 to gradually move during the rotation of the glass master 1 by one rotation, thereby changing the groove from the groove.
Alternatively, it moves by one track from land to land.

When the tracking control circuit 28 moves the objective lens 10, the linear motor control circuit 8
Moves the linear motor 6, that is, the optical head 5, so that the objective lens 10 is located near the center position in the optical head 5.

A data generation circuit 14 is provided at a stage preceding the laser control circuit 13. The data generation circuit 14 converts the format data of the ECC block as the recording data supplied from the error correction circuit 32 described later into the format data of the recording ECC block to which the synchronization code for the ECC block is added.
It has a C block data generation circuit 14a and a modulation circuit 14b that converts (modulates) the recording data from the ECC block data generation circuit 14a by an 8-15 code conversion method or the like.

The data generation circuit 14 is supplied with recording data to which an error correction code (ECC) has been added by an error correction circuit 32. The recording data from the control device 36 as an external device is supplied to the error correction circuit 32 via the interface circuit 45 and the bus 29.

The error correction circuit 32 applies the horizontal and vertical error correction codes to the 32 Kbytes of the recording data supplied from the control device 36 to the recording data in units of 4 Kbytes in units of sectors.
D to generate ECC block format data.

The focusing device has a focusing control circuit 27 and a tracking control circuit 2 respectively.
8, a D / A converter 31 used to transfer data between the linear motor control circuit 8 and the CPU 30 is provided.

The laser control circuit 13, the focusing control circuit 27, the tracking control circuit 28, the linear motor control circuit 8, the motor control circuit 4, the recording signal creation circuit 14 and the like are controlled by the CPU 30 via the bus 29. The CPU 30 performs a predetermined operation in accordance with a cutting start instruction from the operation panel 34 and a program stored in the memory 33.

With the cutting device as described above,
After the cutting process is completed by melting the photoresist of the glass master 1 in accordance with the recording data for the entire surface, development and conductivity are performed to produce a glass master. Using this glass master, a stamper made of nickel or the like is created by electroplating or the like. Using this stamper, the optical disc 100 is prepared by an injection molding method or the like.

Next, an optical disk apparatus for recording data on the optical disk 100 and reproducing the recorded data will be described with reference to FIG. Since the configuration is almost the same as that of the cutting device, the same portions are denoted by the same reference numerals and description thereof will be omitted.

That is, each of the photodetection cells 24a to 24c of the photodetector 24 in a state where focusing and tracking are performed.
The sum signal of the output of 24d, that is, the output signal from the adder 26e, reflects the change in the reflectance from the pits (recording data) formed on the grooves and lands of the track. This signal is supplied to the data reproducing circuit 18, where the E of the ID to be recorded is recorded.
An access permission signal for the CC block is output, and reproduction data for the ECC block of the ID to be reproduced is output.

The reproduced data reproduced by the data reproducing circuit 18 is subjected to error correction by using an error correction code ECC provided by an error correction circuit 32, and then transmitted to a control device as an external device via an interface circuit 35. 3
6 is output.

The laser control circuit 13 changes the intensity of the laser light according to the target optical disk. The data generation circuit 14 outputs recording data to the laser control circuit 13 in response to an access permission signal from the header reading circuit 63 during data recording.

Next, the format of the optical disk will be briefly described. As described above, concentric or spiral tracks of lands and grooves are formed on the optical disc. Further, this track is provided with a plurality of sectors. One sector has a configuration as shown in FIG.

That is, one sector is composed of about 2697 bytes, and is composed of a header area of 128 bytes, a mirror area of 2 bytes, and a recording area of 2567 bytes.

The header area and the mirror area are parts that are recorded (pre-formatted) as uneven shapes before shipment. The recording area only has lands and grooves. The mirror area is used for offset correction of a tracking error signal, timing generation of a land / groove switching signal, and the like.

The recording area is (10 + J / 1)
6) Gap area of byte, guard 1 area of (20 + K) bytes, VFO3 area of 35 bytes, PS of 3 bytes
(Pre-synchronous code) area, 2418-byte data area, 1-byte postamble PA3 area, (55
-K) Guard 2 area of bytes, and (25-J / 1)
6) It is composed of a byte buffer area. Incidentally, J takes an integer of 0 to 15 and K takes an integer of 0 to 7 and takes a random value.

Next, the manufacture of the master of the optical disk of the present invention will be described. It is assumed that the master of the optical disk of the present invention is manufactured by a cutting device shown in FIG.

The laser oscillator 19 (Ar laser output at a wavelength of 458 nm) and the objective lens 10 (NA (numerical aperture)) of the cutting apparatus shown in FIG.
0.9), the laser beam is focused on the photoresist on the glass master 1. The focused spot diameter at this time is
It is 0.46 μm in 1 / e ² and about 0.28 μm in half width. When cutting is performed with a laser beam having such a spot diameter, by adjusting the number of revolutions and the feed pitch of the master, a groove width of approximately 0.1 in accordance with the DVD-RAM standard is obtained.
A substrate of an optical disk for L / G recording having a size of 74 μm and a land width of 0.74 μm can be manufactured. Subsequent to such a cutting process, a substrate of an optical disk manufactured through a series of steps of development, production of a stamper by plating, and molding is referred to as a sample A in the present embodiment.

Next, it is assumed that cutting is performed with a laser beam having an intensity profile as shown in FIG. As a method for generating a side lobe at a predetermined radial position with respect to the peak intensity P1 of the laser spot as described above, for example, Jpn. J. Appl. Phys. Vo
l. 31 (1992) pp. The apodizer technique described in 557-567 is used. That is, by disposing the ring-shaped mask 200 at a position immediately before the laser beam enters the objective lens 10, a laser beam as shown in FIG. 8 can be obtained. Also, the mask 20
By optimizing the size of the diameter of 0 and the size of the hole diameter, the ratio of the peak intensity P1 at the center of the laser spot to the peak intensity P2 of the side lobe, and the peak of the side lobe from the center position of the laser spot The distance L to the position (mountain) can be controlled.

Here, the distance L from the center position of the laser spot to the peak position of the side lobe (actually, since the side lobe has a ring shape, the radius) is fixed to 0.74 μm, and the peak intensity P1 at the center of the laser spot is set. And the intensity ratio between the peak intensity P2 of the side lobe and 1/30, 1/2
A case will be described in which the master recording is performed while changing to 0, 1/10, and 1/5 to manufacture an optical disk substrate.

The steps from (ST1) to (ST5) in FIG. 9 (laser beam irradiation (ST1), melting (ST2), plating (ST3), stamper fabrication (ST4), substrate molding (S
The substrates of the optical disk obtained after T5)) are named sample B, sample C, sample D, and sample E in order of decreasing intensity ratio.

A typical example in which the dent of the land is shallow,
That is, FIG. 10 shows the result of measuring the substrate surface of Sample B by STM (scanning tunnel electron microscope). FIG. 11 shows a typical example in which the dent of the land portion is deep, that is, the result of measuring the substrate surface of sample E by STM. As can be seen from FIG. 11, in the case of the sample E, it can be confirmed that a recess having a depth of about 5 to 20 nm is formed on the surface of the land.

A phase change optical disk having the layer structure shown in FIG. 3 is manufactured on the substrates of the samples A to E manufactured as described above using a vacuum sputtering apparatus (not shown). That is, the first dielectric protection layer 104 is formed on the substrate (102) of each of the samples A to E by the thickness of 180.
0 [angstrom], the adhesive layer 105 for preventing material flow is 100 [angstrom] thick, the phase change recording layer 106 is 200 [angstrom] thick, the adhesive layer 1
07 was formed to a thickness of 100 [angstrom], the second dielectric protection layer 108 was formed to a thickness of 200 [angstrom], and the metal reflective layer 110 was formed to a thickness of 1000 [angstrom]. For the sake of convenience, the optical disks manufactured in this manner correspond to the samples A, B, C, D, and E, and the disks A, B, C,
We will call them D and E.

Next, the overwrite repetition characteristics of the phase change optical disk will be described using the optical disk device shown in FIG. The wavelength of the laser beam output from the laser oscillator 19 of the optical disk device shown in FIG.
0 nm, and the objective lens 10 has an NA of 0.6. Further, it is assumed that the motor 3 is controlled so that the linear velocity is constant at 6.0 m / s at each radial position of the phase change optical disc 100.

In executing the test on the overwrite repetition characteristic of the phase change optical disk, the following control is performed in the optical disk device. First, the laser oscillator 19 is controlled by the laser control circuit 13 so as to perform intensity modulation of the laser beam at a frequency such that the shortest mark length becomes 0.62 μm. Second, the tracking control circuit 28 performs a track jump every one rotation of the optical disk, and controls so that overwriting is always performed on the same track (either land or groove). The overwriting for one rotation of this land or groove was repeated 100,000 times, and the byte error rate (BER) was measured every 10,000 times, and the growth of defects was recorded.

FIG. 12 is a diagram showing the byte error rate when overwriting is repeatedly performed on a predetermined groove. Naturally, the groove is disk A,
Since the shapes of B, C, D, and E should be the same,
It was confirmed that the overwrite repetitive deterioration due to the material flow hardly occurred.

FIG. 13 is a diagram showing the byte error rate when overwriting is repeatedly performed on a predetermined land. In the discs A and B, almost no recess is formed at substantially the center of the surface of the land that is irradiated with the laser beam for reproduction / recording. for that reason,
Degradation starts after about 10,000 overwrites and reaches the upper limit of the byte error rate of 10 ^-4 after 20,000 overwrites.
In the end, it has become ^10-3 .

On the other hand, in the disk C, the byte error rate does not change until about 70,000 overwrites. Also,
Even for 100,000 overwrites, the upper limit of the byte error rate of 10 ^-4 was not exceeded. In the case of disks D and E, the byte error rate hardly changed after 100,000 times of overwriting as in the case of overwriting on the groove. However, as shown in FIG. 11, in the case of the disk E, the center of the land is considerably shaved, and if a concave portion is further formed in the center of the land, the tracking difference signal will be disturbed during tracking by the laser beam. Since it may be judged that there is another groove, the upper limit of the intensity ratio is equivalent to that of the disk E (the peak intensity P1 at the center of the laser spot).
It is considered that the intensity ratio (１ ／ of the peak intensity of the side lobe to 1/5) is appropriate.

As described above, in an optical disc on which L / G recording is performed using a phase-change recording film, when recording the master of the optical disc, the side lobe at a predetermined distance from the center of the laser beam cutting the master. Is formed, the intensity ratio between the center peak intensity of the laser spot and the side lobe peak intensity is set in the range of 1/20 to 1/5, and cutting is performed with the laser beam having the thus set intensity ratio. Thereafter, in a phase change optical disk in which a phase change recording film is formed on a substrate of an optical disk manufactured through development, plating, stamper manufacturing, and molding, overwrite repetition of a land portion, for example, 100,000 times of repetition of a byte. Good characteristics can be maintained without lowering the error rate.

[0061]

According to the present invention, the following optical disk, optical disk master manufacturing apparatus and optical disk manufacturing method can be provided. (1) An optical disc capable of suppressing a material flow in a land provided on the optical disc. In other words, an optical disk that is strong against overwriting.

(2) An optical disk master manufacturing apparatus capable of suppressing a material flow in a land provided on the optical disk.
In other words, an optical disk master manufacturing apparatus that is resistant to overwriting. (3) An optical disc manufacturing method capable of suppressing a material flow in a land provided on an optical disc. In other words, an optical disc manufacturing method that is resistant to overwriting.

[Brief description of the drawings]

FIG. 1 is a diagram showing a layer configuration of a phase change optical disc.

FIG. 2 is a diagram for explaining the principle of deterioration due to material flow caused by repetition of overwriting on a phase change optical disk.

FIG. 3 is a diagram showing a layer configuration of a phase change optical disc on which a substance flow prevention measure is applied.

FIG. 4 is a diagram showing a layer configuration of a phase change optical disc on which a substance flow prevention measure is applied.

FIG. 5 is a diagram showing a schematic configuration of a cutting device for creating a stamper (master) serving as a mold of an optical disc.

FIG. 6 is a diagram showing a schematic configuration of an optical disc device that records data on the optical disc and reproduces data recorded on the optical disc.

FIG. 7 is a diagram showing an example of a sector format.

FIG. 8 is a view showing an intensity profile of a laser beam for cutting a master disc of an optical disc having a depression in a land.

9 is a diagram showing cutting of a master by a laser beam (laser beam having side lobes) having the intensity profile shown in FIG. 8, and further subsequent steps (development, plating, stamper production, molding).

FIG. 10 is a diagram showing a result of measuring a substrate surface by STM when a dent of a land portion is shallow (sample B).

FIG. 11 is a diagram showing the result of measuring the substrate surface by STM when the dent of the land is deep (sample E).

FIG. 12 is a diagram showing a relationship between the number of overwrites in a groove and a byte error rate.

FIG. 13 is a diagram illustrating a relationship between the number of overwrites on a land and a byte error rate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass master disk 10 ... Objective lens 100 ... Optical disk 102 ... Substrate 104 ... 1st dielectric protection layer 106 ... Phase change recording layer 108 ... 2nd dielectric protection layer 110 ... Metal reflection layer 112 ... UV coin resin protection layer 200 ... ring

Claims (11)

[Claims] 1. A method according to claim 1, further comprising a concentric or spiral land and groove tracks, wherein at least the land has information by utilizing a reversible phase change between an amorphous state and a crystal state when irradiated with a light beam. An optical disc characterized by having a recess along the track direction substantially at the center of the surface of the land receiving the light beam irradiation. 2. The optical disk according to claim 1, wherein the depth of the recess is 5 to 20 nm. 3. It has concentric or spiral tracks of lands and grooves, and records information by utilizing a reversible phase change between amorphous and crystalline when irradiated with a light beam. An optical disk master manufacturing apparatus for manufacturing an optical disk master, comprising: manufacturing an optical disk master having a recess along a track direction substantially at a center of a surface of the land to be irradiated with a light beam. apparatus. 4. The apparatus according to claim 3, wherein the depth of the recess is 5 to 20 nm. 5. It has concentric or spiral land and groove tracks, and records information by utilizing a reversible phase change between amorphous and crystalline when irradiated with a light beam. In an optical disc master manufacturing apparatus for manufacturing an optical disc master, an irradiation unit for irradiating a light beam for cutting the master, and a side lobe generating unit for generating a predetermined side lobe in the light beam irradiated by the irradiation unit An optical disc master manufacturing apparatus, comprising: a control unit that controls cutting of the master by a light beam having a predetermined side lobe generated by the side lobe generating unit. 6. A peak value of a light intensity of a side side lobe of a light beam with respect to a peak value of a light intensity at a center of a light beam irradiated by the irradiation means.
6. The optical disk master manufacturing apparatus according to claim 5, wherein: 7. It has concentric or spiral tracks of lands and grooves, and records information by utilizing a reversible phase change between amorphous and crystalline when irradiated with a light beam. An optical disk manufacturing method for manufacturing an optical disk, comprising: manufacturing an optical disk having a depression along a track direction substantially at a center of a surface of the land that is irradiated with a light beam. 8. It has concentric or spiral tracks of lands and grooves, and records information by utilizing a reversible phase change between amorphous and crystalline when irradiated with a light beam. An optical disk manufacturing method for manufacturing an optical disk, comprising: manufacturing a master disk of an optical disk having a recess along a track direction at substantially the center of a surface of the land receiving light beam irradiation; manufacturing an optical disk based on the manufactured master disk; An optical disk manufacturing method characterized by the above-mentioned. 9. The method according to claim 7, wherein the depth of the recess is 5 to 20 nm. 10. It has concentric or spiral tracks of lands and grooves, and records information by utilizing a reversible phase change between amorphous and crystalline when irradiated with a light beam. In an optical disk manufacturing method for manufacturing an optical disk, a light beam for cutting the master of the optical disk is irradiated, a predetermined side lobe is generated in the irradiated light beam, and a light beam generated by the predetermined side lobe is used. An optical disc manufacturing method, comprising: controlling the cutting of the master, and manufacturing an optical disc based on the master manufactured by cutting under the control. 11. A light source according to claim 1, wherein the peak value of the light intensity of the side lobe of the light beam is 1/20 to 1/5 of the peak value of the light intensity at the center of the irradiated light beam. 11. The method for manufacturing an optical disk according to claim 10, wherein: