JP2001148140A - Rewritable compact disc and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rewritable compact disc having a rewritable area and a read-only area which are compatible with a CD-RW on one medium surface, and a method of manufacturing the same. SOLUTION: This is a rewritable compact disk, having a RAM area 105 and a ROM area 104 on the same disk surface, wherein a phase change type recording layer has a RAM area and a ROM.
Provided in both the area and the RAM area, a wobble groove is provided in the RAM area, information can be recorded by irradiating a recording light to form an amorphous mark, and information is recorded in a ROM area by a pre-pit row. When measured using an optical pickup having a wavelength of 770 to 790 nm and an objective lens numerical aperture of 0.49 to 0.51, the ratio | I ₁ −I ₂ | of the push-pull signal value before and after recording in the RAM area / | I ₁ -I ₂ | _a is 1.
05 to 2.0 or the ratio | I ₁ −I ₂ | _a / | I ₁ −I ₂ | _ROM of the push-pull signal value after recording in the RAM area to the push-pull signal value in the ROM area. It is 0.78 or more and 1.3 or less.

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 and reproducing information by a laser beam and a method for manufacturing the same, and more particularly to a read-only ROM area and a writable RAM.
The present invention relates to a rewritable compact disc having an area and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in addition to music CDs and CD-ROMs, CDs have been used as recordable media compatible therewith.
-R (CD-Recordable) and CD-RW (CD-Rewritable) have been commercialized and are becoming widespread. These groups are called the CD family, and CDDA and CD-
ROM, CD-ROMXA, CDV, CD-I, CD-
MIDI and the like. CDDA is a so-called music CD. In the following description, these may be collectively referred to as a read-only CD.

[0003] In these read-only CDs, an uneven pit array having information is formed in advance on a substrate made of translucent polycarbonate or the like by means of a press or the like, and a precious metal or Al or the like is formed on the surface where the pits are formed. And a protective layer made of a photocurable resin is formed thereon. These reproduction-only CDs are widely used for storing and reproducing music, images, data, programs, and the like. The specification relating to the recording and reproduction signals of the CD is defined as a CD standard, and a reproducing apparatus conforming to the standard is widely used as a CD player.

On the other hand, CD-Rs and CD-RWs are writable media by users. CD-R is a CD-ROM drive or audio CD mounted on a personal computer.
Although it can be played back on a player, it can only be written once, and once recorded data cannot be erased. on the other hand,
CD-RWs have a lower reflectance than read-only CDs,
-Can only be played on RW compatible drives, but CD-R
Unlike this, data can be rewritten, and data can be rewritten 1000 times or more.

[0005] This CD-RW is a kind of phase-change type optical disk, and an inorganic protective layer, a phase-change type recording layer, an inorganic protective layer, and a reflective layer are laminated in this order on a transparent resin substrate in which guide grooves are formed in advance. And a protective layer made of a photocurable resin is further formed thereon. The entire surface of the recording layer is once brought into a crystalline state, which is then put into an erased state. Recording is performed by irradiating a high-power laser beam to the recording layer on the guide groove.
The crystalline state of the recording layer is changed to form an amorphous mark, which causes a change in reflectance with respect to a portion not irradiated with the laser. Irradiate low power laser light to the formed mark part,
The recorded information can be reproduced by detecting a change in the reflectance. That is, the recording marks have substantially the same function as the pits in the read-only CD.

[0006] A read-only CD has the advantage of being able to supply inexpensive and large quantities of application software and the like, but cannot perform writing. On the other hand, as described above, C
D-RW is a writable, large-capacity recording medium whose format is standardized, has excellent compatibility with read-only CDs, and is very easy to handle. It is not suitable for low-cost and large-volume supply.

[0007]

In general, when a CD-RW writer is mounted on a personal computer, a CD-RW is used.
Usually, ROM drive etc. are not installed at the same time,
Since only a CD-RW writer is mounted, C
In many cases, D and CD-RW cannot be used simultaneously. In this case, data created and processed using application software distributed on a read-only CD
Once the read-only CD is removed from the drive, the CD-R
It cannot be recorded unless exchanged for W.

For this reason, there is a problem that a complicated procedure must be used to record data on a CD-RW while using application software distributed on a CD-ROM. To solve this problem, CD-
There is a method in which application software or the like is recorded on the RW in advance by a recording device and distributed. However, this method has a problem that mass production of the medium is difficult, and a problem that there is a possibility that the application software once recorded is erroneously erased, and is not a practical solution.

Japanese Patent Publication No. 7-122935 discloses a technique relating to an optical information recording medium having a ROM area and a RAM area on the same surface. However, the technique disclosed in this publication is to form an organic material recording film as a recording layer only in a RAM area as a recordable area. By changing the structure of the films formed in the RAM area and the ROM area in this way, it is easy to separately control the signal values read from both areas, but at the time of film formation, a mask jig is used for each substrate. In addition, it is necessary to form a film covering the ROM area, which is not preferable in manufacturing. If the position or size of the ROM area changes, the mask also needs to be changed accordingly, which is not preferable in this respect.

[0010] Further, the column of (Problem to be Solved by the Invention) in this publication describes "a ROM area which is a read-only area and a RAM which is a recordable area as disclosed in Japanese Patent Application No. 2-36190.
We have applied for an optical disk that has a recording layer made of an organic material over the entire area and is compatible with a compact disk. " However, the recording layer is made of an organic material,
Since the dye layer is also formed in the area, the ROM area is susceptible to the photobleaching of the dye, as described in the column of (Problem to be Solved by the Invention) in this publication. Not preferred.

Japanese Patent Publication No. 7-70089 discloses that
There is disclosed a technology relating to an optical information carrying disk in which a recording layer on which information is recorded by a change in a crystal state by light irradiation is provided on a surface of a substrate on which information is recorded by uneven dots. However, this technology has a so-called phase-change type recording layer, which is provided with a phase-change type recording layer instead of a reflective layer in order to enable partial correction, update and addition of information. And ROM on the same side
It does not form an area and a RAM area.

The present invention has been made in view of the above-described problems, and has been made in consideration of one CD while maintaining compatibility with a CD-RW.
-It is an object of the present invention to provide a rewritable compact disc having a ROM area and a RAM area, and a method of manufacturing the same, which can realize both the use of application software and the like and the recording of data with a RW writer.

[0013]

The first gist of the present invention is as follows.
A rewritable compact disc having at least a phase-change recording layer on a substrate, having a recordable, erasable, reproducible RAM area and a reproducible ROM area on the same disc surface, The phase change type recording layer is provided in both the RAM area and the ROM area, and a wobble groove is provided in the RAM area. EFM-modulated information can be recorded by irradiating recording light and forming an amorphous mark in the groove by setting an erasing state, setting an amorphous portion to a recording state, and irradiating a recording light. , EFM-modulated information is recorded by a pre-pit string, and a wavelength of 770
-790 nm, numerical aperture of objective lens 0.49-0.51
When the measurement is performed using the optical pickup _{No. 1,} the ratio | I ₁ −I ₂ | / | I ₁ −I ₂ | _a of the push-pull signal value before and after recording the EFM modulated signal in the RAM area is 1 .05
2.0 or less, or the ratio | I ₁ −I ₂ | _a / | I ₁ −I ₂ | of the push-pull signal value after recording in the RAM area and the push-pull signal value in the ROM area. _ROM is 0.78
There is a rewritable compact disc characterized by being 1.3 or less.

In particular, one of the EFM modulated signals in the ROM area is
The 1T signal modulation degree is preferably 0.55 or more and 0.95 or less. The ratio of the 3T signal modulation and 11T signal degree of modulation of EFM-modulated signal of the ROM area (m ₃ /
m ₁₁ ) It is preferable that the _ROM is 0.45 or more. Further, it is preferable that the modulation degree of the 11T signal of the EFM modulation signal in the RAM area is 0.60 or more and 0.90 or less.

The ratio (m ₃ / m ₁₁ ) between the 3T signal modulation degree and the 11T signal modulation degree of the EFM modulation signal in the RAM area is _RAM
It is preferably 0.45 or more. Further, the ROM
Ratio of the maximum reflectance of the RAM area to the RAM area R _topROM / R
_{The topRAM preferably} has a _size of 0.7 or more and 1.45 or less. Further, it is preferable that the value of the radial contrast of the ROM area is 0.30 or more and 0.60 or less.

Preferably, a pre-pit string in the ROM area
Have wobbles. And the ROM area
Wobble signal value NWS obtained from the wobble of the area
_{RO M}Is preferably 0.035 or more and 0.060 or less.
Good. The pre-pit row in the ROM area is
The depth is 60 to 100 nm and the pit width is 0.45
It is preferably about 0.70 μm.

Further, the wobble groove in the RAM area has a groove depth of 30 to 50 nm and a groove width of 0.40 to 0.2.
Preferably it is 60 μm. The second gist of the present invention is that
A rewritable compact disc having at least a phase-change recording layer on a substrate, having a recordable, erasable, reproducible RAM area and a reproducible ROM area on the same disc surface, The phase change recording layer is provided in both the RAM area and the ROM area, and a groove (groove having a wobble) is provided in the RAM area. To an unrecorded state / erased state, an amorphous portion to a recorded state, and irradiating a recording light to form an amorphous mark in the groove, so that EFM-modulated information can be recorded. In the ROM area, E
The FM-modulated information is recorded in a pre-pit row, and the pre-pit row in the ROM area has a pit depth of 60
１００100 nm and a pit width of 0.45 to 0.70
The groove (wobble groove) in the RAM area has a groove depth of 30 to 50 nm and a groove width of 0.40 to 0.6.
A rewritable compact disc characterized by being 0 μm.

A third aspect of the present invention is to provide a rewritable compact disc as a preferred method for manufacturing a rewritable compact disc by irradiating a resist film formed on a substrate with a laser beam in accordance with a prepit row and a groove to be formed. Then, a master master having the pre-pit rows and grooves formed thereon by developing was prepared, a stamper was formed based on the master master, and a substrate provided with the pre-pit rows and grooves was formed based on the stamper. After that, in the manufacturing method of providing the phase-change recording layer, when irradiating the resist film with laser light in accordance with the groove, the resist film may be irradiated in a direction perpendicular to the traveling direction of laser light by 2.5
A method for manufacturing a rewritable compact disc, comprising irradiating and exposing while oscillating at a speed of × 10 ⁶ times / m or more and 25 × 10 ⁶ times / m or less.

A fourth gist of the present invention is that, as another preferable method of manufacturing this rewritable compact disc, a laser beam is irradiated according to a prepit array and a groove to be formed on a resist film formed on a substrate. Exposure and development to create a master master with the pre-pit rows and grooves formed,
A stamper is created based on the master master, and further, based on the stamper, after forming a substrate provided with the pre-pit row and the groove, a manufacturing method of providing a phase-change recording layer is performed according to the groove. When irradiating the resist film with laser light, it is characterized in that a plurality of laser lights are irradiated and exposed so that adjacent laser beams partially overlap in a direction perpendicular to the traveling direction of the laser light. A method for manufacturing a rewritable compact disc.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of an arrangement of a non-data area and a data area of a CD-RW as a rewritable compact disc to which the present invention is applied. The CD-RW (simply called a disk) 10 shown in FIG.
0 is an optically reproducible or recordable recording medium,
A management area 101 and a user area 102 are provided.

The management area 101 is an area that can be reproduced by a drive device (not shown) and cannot be accessed by a user.
libArea (Libration Area) and PMA (Program Memory Area). Here, the PCA is an area where information for adjusting the intensity of the laser when data is written is recorded. In the PMA, for example, a recording start address at the time of additional recording is temporarily recorded.

Further, the user area 102 is an area that can be read by the drive device and is an area where the user can arbitrarily access the area. This user area 102
Is a lead-in area 103 for storing a lead-in.
A read-only ROM area 104 from which a drive device (not shown) can only read data; and a RAM from which a drive device (not shown) can record, erase, and reproduce data.
It comprises an area 105 and a lead-out area 106 for storing a lead-out. Note that the ROM area 104 and the RAM area 105 may be collectively referred to as a data area (program area).

In the ROM area 104, EFM-modulated information is recorded in a pre-pit string. The information to be recorded in the ROM area 104 may be, for example, application software or driver software, but the type is not particularly limited. For example, the special C
It may be D-RW medium information, authentication information, or the like. CD
-RW has a problem that the protection of such a copyrighted work is not thorough because the user can easily copy the data of the copyrighted work such as music, a movie, or a computer program. As a method of protecting such copyrighted data, a usage fee is added to the CD-RW in advance, authentication information and the like are recorded in the ROM area 104, and the CD-RW with the authentication is recorded on such a CD-RW. As far as possible, there is a method that allows copying of copyrighted data.

On the other hand, the RAM area 105 has a phase change type recording layer, and the crystal state portion of the phase change type recording layer is set to an unrecorded / erased state, and the amorphous portion is set to a recorded state. It is. The RAM area 105 is provided with a guide groove (wobble groove) having wobbles, and while guiding along the wobble groove, irradiates the phase-change recording layer with recording light to form an amorphous mark (recording). By forming the mark, information that has been subjected to EFM modulation is recorded.

Although the ROM area 104 is located at the innermost circumference of the data area in FIG. 1, it is not always necessary to set it at the innermost circumference. However, in consideration of accessibility and simplicity of manufacture, it is preferable to set the data area to the innermost circumference or the outermost circumference. If importance is placed on compatibility with a CD-RW having only the RAM area, it is preferable that the innermost circumference of the data area be the RAM area.

The ROM area 104 and the RAM area 10
It is preferable to provide a buffer area not used for data recording / reproducing at the boundary portion with No. 5. As a result, the logical connection of data can be broken, and it is possible to prevent tracking and recording / reproduction from becoming impossible due to differences in groove / pit signal characteristics between the two regions. As a preferred example, there is a method of using a multi-session method defined in ISO9660 and setting a ROM area and a RAM area as separate sessions. In this case, for example, from the innermost circumference, a lead-in area, a ROM area, a lead-out area,
Lead-in area, RAM area, lead-out area ...
Therefore, the ROM area and RA
A lead-out area and a lead-in area are always arranged between the M area and can be used as a buffer area. Normally, the lead-out area and the lead-in area as buffer areas have a length equivalent to one minute (reproduction takes about one minute) during reproduction at a linear velocity of 1.2 m / s. It is enough.

Alternatively, a UDF format (Universa
l Disk Format), a specific packet group can be allocated to the ROM area. By the way, in the CD-RW 100 according to the present embodiment, a phase-change recording layer is provided not only in the RAM area 105 but also in the ROM area 104.
Specifically, as shown in FIG. 2, at least the phase change recording layer 52 is provided on the substrate 50 over the entire management area 101 and the user area 102. Preferably, the substrate 50
A protective layer 51, a phase-change recording layer 52, a protective layer 53,
A reflective layer 54 is provided in this order, and a protective coat layer 55 such as an ultraviolet-curable resin layer or a thermosetting resin layer is provided on the uppermost layer in order to prevent direct contact with air and prevent damage due to contact with foreign matter. Is provided with a thickness of about 1 μm to about several hundred μm.

As described above, in the present embodiment, a layer having the same configuration as that of the RAM area 105 is provided in the ROM area 104 as well. As shown in FIG. 2, a plurality of pits (pre-pits) 6 are provided in the ROM area 104 of the substrate 50.
A pit row (pre-pit row) composed of 0s is formed, and a guide groove 61 is formed in the RAM area 105.

By the way, in order to record / reproduce an optical disk having a ROM area 104 and a RAM area 105 with a single drive, the ROM area 104 and the RAM area 105 are required.
It is necessary to optimize the groove signal characteristics (for example, tracking signal characteristics) and reproduction signal characteristics of each of the above. In addition, at the switching point between the ROM area 104 and the RAM area 105, sufficient continuity of the groove signal and the reproduction signal is ensured, and the groove signal characteristic (for example, tracking signal characteristic) and the reproduction signal characteristic are optimized. Is also important.

Hereafter, various signals in this embodiment are measured using an optical pickup having a wavelength of 770 nm to 790 nm and an objective lens numerical aperture (objective lens aperture ratio) NA of 0.49 to 0.51. I do. These measurement conditions basically followed the CD-RW Orange Book standard. However, the numerical aperture NA of the objective lens is 0.44 to
0.49-0.51 instead of 0.46 (about 0.45)
(About 0.50) was used.

As a result of various studies by the present inventors, various
Signal characteristics (tracking signal characteristics)
Indicates that the push-pull signal value is the most important characteristic.
won. That is, the EFM conversion in the RAM area 105 is performed.
The push-pull signal value before recording the tone signal and the
Ratio to push-pull signal value | I₁-I_Two| / | I₁-I_Two|
_aIs preferably 1.05 or more and 2.0 or less.

With such a range, the RAM
Groove signal characteristics in the region 105 (tracking signal characteristics
) Can be optimized. In addition, playback signal characteristics
Optimality will also be optimized. Also, the RAM area 105
Push-pull signal value after recording EFM modulated signal at
Of the push-pull signal value of ROM area 104 to | I
₁-I_Two|_a/ | I₁-I _Two|_ROMIs 0.78 or more and 1.3 or less
Is preferred.

With such a range, the ROM
Sufficient continuity of signals (groove signals and reproduction signals) can be obtained even at the transition between the area 104 and the RAM area 105, so that operation is possible within the dynamic range of the tracking servo of the drive (drive device). The reproduction of the ROM area 104 and the recording / reproduction of the RAM area 105 of the drive device can be continuously performed. Thereby, the groove signal characteristic (tracking signal characteristic) at the switching point between the ROM area 104 and the RAM area 105.
In addition, it is possible to optimize the reproduction signal characteristics.

When setting so as to satisfy any of the above ranges, the push-pull signal value before recording the EFM modulated signal in the RAM area 105 and the R
Ratio to push-pull signal value of OM region 104 | I ₁ −I ₂
| / | I ₁ -I ₂ | _ROM is 0.82 (1.05 × 0.7
8) to 2.6 (2.0 × 1.3) are preferable, but within this range, those having 1.05 or more and 2.0 or less are most preferable.

As described above, the numerical aperture of the objective lens NA
Is changed from 0.45 to 0.50, so that the same laser light tends to be narrowed down and the diameter of the laser beam irradiated on the disk 100 tends to be small. For this reason, each push-pull signal value tends to be slightly larger, but here, since these values are divided and the ratio of these values is obtained, each push-pull signal value is changed by changing the numerical aperture NA of the objective lens. There is no problem even if the value changes.

Here, the push-pull signal value will be described with reference to FIG. Here, the reproduction of the optical disk is usually performed by receiving the reflected light of the light spot that moves integrally with the head or the pickup, but the tracking error signal is divided into two parts in the radial direction of the optical disk. First photodetector consisting of light receiving element
Output I ₁ from the light receiving element, obtained by processing in the signal processing circuit and an output I ₂ from the second light receiving element. FIG. 3 shows an I ₁ -I ₂ signal obtained by performing arithmetic processing on a reproduction signal obtained when reproduction is performed without tracking (that is, a reproduction signal when there is no tracking error).

Before recording in the RAM area 105, the light amount of the light reflected from the disc 100
The absolute value of the difference between the signal values measured by the divided light receiving elements is |
It is represented by I ₁ -I ₂ |. After recording in the RAM area 105, the absolute value of the difference between the signal values obtained by measuring the light amount of the light reflected from the disk 100 by the light receiving element divided into _two is represented by | I ₁ −I ₂ | _a .

In the ROM area 104, the disk 10
The absolute value of the difference between the signal values obtained by measuring the amount of light reflected from 0 with the light receiving element divided into _two is represented by | I ₁ −I ₂ | _ROM . Here, | I ₁ −I ₂ | _a and | I ₁ −I ₂ | _ROM are
Since the value greatly fluctuates depending on the recorded signal, the output signal is used as a signal once obtained through a 5 kHz low-pass filter.

These correspond to push-pull signal values before normalization, respectively.
The ratio of the push-pull signal value before recording the EFM modulated signal to the push-pull signal value after recording at | I ₁ −
I ₂ | / | I ₁ −I ₂ | _a , and the RAM area 1
The ratio between the push-pull signal value after recording the EFM modulated signal in 05 and the push-pull signal value in the ROM area 104 can be represented by | I ₁ −I ₂ | _a / | I ₁ −I ₂ | _ROM .

Since the push-pull signal value varies depending on the radial position from the center of the groove (or pit),
The comparison as described above is performed between the maximum values of the respective signal values. By the way, the push-pull signal value changes depending on the layer configuration such as the recording layer and the external environment, but such a change can be eliminated by normalizing by dividing by another signal so that the signal value itself can be evaluated. Become.

Next, the push-pull signal value after the standardization will be described. First, 0.1μ radially from the center of the groove
I ₁ -I ₂ | | when deviates m (in FIG. 3, corresponds to the PP _raw), the value divided by the groove signal level I _g before recording in the RAM area 105 | I ₁ -I ₂ | / I _g , the groove signal level I
_This is referred to as a push-pull signal value before recording normalized by _g .
Here, the groove signal level I _g, corresponding to a bottom level of I ₁ -I ₂ signal.

Also, 0.1 μm from the center of the groove in the radial direction.
The value | I ₁ −I ₂ | obtained by dividing | I ₁ −I ₂ | _a (corresponding to PP _raw in FIG. 3) by the average groove signal level _Iga after recording in the RAM area 105. _a / I _ga is referred to as a push-pull signal value after recording normalized by the average groove signal level I _ga . Here, the average groove signal level _Iga after recording is
Since the groove signal level greatly fluctuates depending on the recorded signal, the bottom level of the signal obtained by temporarily passing the (I ₁ −I ₂ ) _a signal through a 5 kHz low-pass filter is used.

The ratio between the push-pull signal value before recording the EFM modulated signal in the RAM area 105 and the push-pull signal value after recording is the ratio of the above-mentioned normalized value (| I ₁ −I ₂ | _{/ I g) / (| I} 1 -I 2 | may be used _a / I _ga) becomes the value. In this case, (| I ₁ −I ₂ |
/ I _g ) / (| I ₁ −I ₂ | _a / I _ga ) is 0.5 or more and 1.3.
It is preferred that:

Also, 0.1 μm from the center of the groove in the radial direction.
| I when deviated₁-I_Two|_a(In FIG. 3, PP_rawPhase
EFM modulated signal after recording in the RAM area 105.
Maximum level I of the reproduced signal corresponding to the 11T signal of the signal
_topRAMDivided by | I₁-I_Two| _a/ I_topRAMThe maximum
Issue level I_topRAMPush-pull signal after recording standardized by
This is referred to as a signal value.

The maximum signal level I of the RAM area 105
_topRAMPush-pull signal value | I after recording normalized by I₁
-I_Two|_a/ I_topRAMIs usually 0.070 or more and 0.12
0 or less. More preferably 0.080 or more and 0.10
0 or less. In the ROM area 104, a pit row
When the distance from the center of 60 is 0.1 μm in the radial direction
｜ I₁-I_Two|_ROM(In FIG. 3, PP_raw), R
It corresponds to the 11T signal of the EFM modulated signal in the OM area 104.
The maximum level of the reproduced signal_{to pROM}Divided by | I₁−
I_Two|_ROM/ I_topROMWith the maximum signal level I_topROMIn standard
Called the push-pull signal value of the ROM area 104
You.

Push-pull signal value | I ₁ −I ₂ | in ROM area 104 standardized by this maximum signal level I _topROM
ROM / I _topROM is usually 0.020 or more (more preferably 0.040 or more) and 0.070 or less. here,
The reason why the range of the push-pull signal value standardized by the maximum signal level is set as described above is that if the push-pull signal value is too small, tracking will not be performed normally, but if it is too large, there is a problem. is there. In other words, the drive attempts to return the optical head to the normal tracking position with a force proportional to the push-pull signal value. If the push-pull signal value is too large, overshoot increases and tracking to the normal position becomes difficult. It is.

Meanwhile, among the groove signal characteristics (for example, tracking signal characteristics), the value of the radial contrast is also important. This radial contrast value is desirably 0.30 or more and 0.60 or less in the ROM area 104. If it exceeds this range, it is difficult to accurately perform track counting during seeking. Also, if the radial contrast value is too large, it may not be recognized as a track depending on the drive, but may be erroneously recognized as a scratch.

[0048] Preferably, the radial contrast value RC _b of the guide groove before recording in the RAM area 105 is 0.0
5 in such a manner that above, the radial contrast value RC _a of the guide groove after recording an EFM-modulated signal is 0.30 to 0.60 (more preferably 0.55 or less) so that the. Thereby, continuity with the radial contrast value in the ROM area 104 can be maintained.

The ROM area 104 and the RAM area 10
5 and the radial contrast values after recording in the RAM area 105 are represented by the following equations (1), (2), and (3), respectively.
Defined by

[0050]

(Equation 1)

The land level and the pit level of the reproduced signal are set to I _LAND and I _PIT respectively, and the RAM area 10
5, the land level and groove level of the groove signal before recording are I _l and I _g , respectively, and the land level and groove level of the groove signal after recording in the RAM area 105 are I _la and I _ga , respectively. The reproduction signal in the ROM area 104 and the groove signal in the RAM area 105 are average signals after the reproduction signal and the groove signal have been once passed through a 5 kHz low-pass filter. In each case, it is assumed that the measurement was performed without tracking.

Next, regarding the reproduction signal characteristics, the 11T signal modulation degree of the EFM modulation signal is the most important, and the 11T signal modulation degree of the EFM modulation signal in the ROM area 104 is 0.5.
5 or more and 0.95 or less (more preferably 0.60 or more), and the 11T signal modulation degree of the EFM modulation signal in the RAM area 105 is 0.60 or more and 0.90 or less (more preferably 0.80 or less). Is preferred. This allows RO
Information can be reliably read in any of the M area 104 and the RAM area 105,
Necessary information reproducing ability can be secured.

Here, regarding the 11T signal modulation degree m ₁₁ ,
This will be described with reference to FIG. FIG. 4 shows that when the disc 100 is reproduced with tracking,
The sum I ₁ + I ₂ of signals obtained by measuring the amount of light reflected from the light receiving element by the light receiving element divided into _two is shown. Here, 11
The amplitude of the reproduced signal corresponding to the T signal is defined as I _11, and the maximum level of the reproduced signal corresponding to the 11T signal is defined as I _top (= I
_{11, LAND} ), I ₁₁ / I _top becomes 11T signal modulation degree m ₁₁ .

The 11T signal modulation degree m _{11 in the} ROM area 104
Is _I11ROM / _ItopROM , and 1 of the RAM area 105
The 1T signal modulation degree m ₁₁ is I _11RAM / I _topRAM . R
In any area of the OM region 104 and the RAM area 105, 11T signal modulation m ₁₁ is preferably set to be 0.55 or more. This is because it becomes impossible to read the correct pattern when 11T signal modulation m ₁₁ is too small. It is not preferable to increase the 11T signal modulation degree m ₁₁ in the ROM area 104 beyond 0.95. This, 11T signal modulation m ₁₁ is saturated signal strength when expanded signal with too large drive, it becomes impossible to again read the exact pattern.

On the other hand, it is not preferable to a 11T signal modulation m ₁₁ in the RAM area 105 is increased beyond 0.90. That is, in the RAM area 105, when the amplitude of the reproduction signal is increased, the reproduction signal amplitude of the long mark such as 11T or 10T increases, but the reproduction signal level of the short mark such as 3T or 4T decreases overall, and The reproduction signal amplitudes I ₃ and I ₄ tend not to increase. If the reproduction signal of the long mark is increased while the reproduction signal of the short mark is small, the slice level I _slice for detecting the signal from the reproduction waveform becomes too low, and the mark may not be reproduced and an accurate pattern may not be read. .

This condition is important for maintaining the continuity of the reproduction signal characteristics in both the ROM area 104 and the RAM area 105. More preferably, the EF of the ROM area 104
The ratio (m ₃ / m ₁₁ ) between the 3T signal modulation degree and the 11T signal modulation degree of the M modulation signal _ROM is 0.45 or more. Also, RAM
3T signal modulation degree of EFM modulation signal in area 105 and 11T
Ratio with signal modulation (m ₃ / m ₁₁ ) _RAM is 0.45 or more.

As described above, the 11T signal modulation degree m ₁₁ is m
₁₁ = I ₁₁ / I _top and the 3T signal modulation degree m ₃ is m ₃ =
Since it is expressed by I ₃ / I _top , the 3T signal modulation degrees m ₃ and 11
The ratio (m ₃ / m ₁₁ ) to the T signal modulation degree m ₁₁ is the ratio (I ₃ / I ₁₁ ) between the reproduced signal amplitude I ₃ corresponding to the 3T signal and the reproduced signal amplitude I ₁₁ corresponding to the 11T signal. Equally, this can be substituted.

[0058] The ratio of the 3T signal modulation m ₃ and 11T signal degree of modulation _{m 11 (m 3 / m 11} ), or the reproduction signal amplitude corresponding to the reproduction signal amplitude I ₃ and 11T signal corresponding to the 3T signal the ratio of _{I 11 (I 3 / I 11} ) represents the ratio between the largest signal and the most small amplitude signal in the reproduced signal is an index representing the resolution of the reproduced signal. Here, the ratio (m ₃ / m ₁₁ ) between the 3T signal modulation m ₃ and the 11T signal modulation m ₁₁ , or the reproduction signal amplitude I ₃ corresponding to the 3T signal and the reproduction signal amplitude I ₁₁ corresponding to the 11T signal. (I ₃ / I ₁₁ )
Is preferably 0.45 or more (more preferably 0.50 or more) in any of the ROM area 104 and the RAM area 105. This is because if the resolution is too small, it becomes difficult to read out an accurate pattern.

[0059] The ratio of the 3T signal modulation m ₃ and 11T signal degree of modulation _{m 11 (m 3 / m 11} ), or the reproduction signal amplitude corresponding to the reproduction signal amplitude I ₃ and 11T signal corresponding to the 3T signal The ratio to I ₁₁ (I ₃ / I ₁₁ ) has no particular upper limit.
Although preferably larger, since I ₃ will not be greater than I _11, will be limited in effect, to 1 or less. More preferably, the asymmetry value defined by the following equation is set as the specific range.

[0060]

(Equation 2)

That is, in the ROM area 104, the asymmetry value is -20% or more and 20% or less, and the RAM area 1
05 after recording the EFM modulated signal is -1.
It is preferably from 5% to 5%. Furthermore, ROM
The ratio R of the maximum reflectance between the area 104 and the RAM area 105
_It is preferable that _topROM / R _topRAM is 0.7 or more and 1.45 or less. More preferably, it is set to 0.85 or more and 1.20 or less. In this case, the ROM area 104 and the RAM area 1
It is preferable that the maximum reflectivities R _topROM and R _topRAM in both regions of _No. 05 be 15% or more and 25% or less.

As described above, the ROM area 104 and the RAM area
Ratio R of the maximum reflectance with the region 105_{topR OM}/ R_topRAMIs 0.
Drive within 7 to 1.45
Continuously in the ROM area 104 and the RAM area 105.
Even if it is accessed, playback in ROM area 104
Signal and the reproduction signal in the RAM area 105.
Read the correct pattern
You can get out.

In this case, a gap (closed track; for example, 2 × 75 × 2 kilobytes) is provided at the boundary between the ROM area 104 and the RAM area 105 so that the reproduction time by the drive is longer than the time required for gain adjustment. Or a lead-in area. As a result, even when the RAM area 105 is continuously accessed from the ROM area 104, the R
The gain can be surely adjusted within the transition time to the AM area 105, that is, the time when the optical pickup of the driver moves the gap or the lead-in area.

Here, the maximum reflectance R _top is the reflectance when the reproduced signal corresponding to the 11T signal of the EFM modulation signal has the maximum level, and is expressed by the following equation. R _top = R ₀ × I _top / I ₀ (5) where R ₀ is the reflectance at the mirror portion on the disk, I ₀ is the reproduction signal level at the mirror portion, and I _top is the EFM modulation signal. 1
This is the maximum level of the reproduced signal corresponding to the 1T signal.

Note that, as described above, the numerical aperture of the objective lens NA
Is changed from 0.45 to 0.50, and even if the same laser light is used, there is a tendency that the diameter of the laser beam irradiated on the disc 100 is reduced.
The degree of 1T signal modulation tends to be slightly large, and specifically shifts to about 0.05, which is not a problem. In this case, the maximum reflectances R _topROM and R _topRAM hardly change. Also, the radial contrast and the normalized wobble signal value NWS hardly change.

Incidentally, the CD-RW recording system includes a system for continuously recording from the inner periphery to the outer periphery and a packet write system for discrete recording like a floppy (registered trademark) disk. Generally, the packet write method is more desirable for use as an external storage device of a computer. However, in the packet write method, since the above-described gap portion and lead-in area are not provided, the drive is RO
When the M area 104 and the RAM area 105 are continuously accessed, it is difficult to adjust the gain.

In this case, as described later, the ROM area 1
04 is provided with a groove to reduce the reflectance of the ROM area 104, and the ratio R _topROM / R _topRAM of the maximum reflectance R _topROM of the ROM area 104 and the maximum reflectance R _topRAM of the RAM area 105.
To a more preferable range (0.9 or more and 1.10 or less), even when the drive continuously accesses the ROM area 104 and the RAM area 105 without performing the above-described gain adjustment. An accurate pattern can be read.

According to this, since the above-described gap section and lead-in area are not required for gain adjustment, the ROM area 104 and the RAM area 105 are divided into one C
When provided in the D-RW and used as an external storage device of a computer, the packet write method can be adopted. As described above, the reflectivity of the ROM area 104 is reduced, and the maximum reflectivity R _topROM of the ROM area 104 and the RAM area 1 are reduced.
In _{order to set} the ratio R _topROM / R _topRAM of the maximum reflectance R _topRAM of 05 to a more preferable range (0.9 or more and 1.10 or less),
In order to form a groove in the ROM area 104, for example, as shown in FIGS. 5, 6A and 6B, the space between the prepits 60 in the prepit row in the ROM area 104 is not made flat. The pre-pits may be connected by a groove (for example, a shallow groove) 70. That is, as shown in FIGS. 5, 6A and 6B, the grooves 70 may be formed so as to overlap the pit rows 60 in the ROM area 104.

Preferably, the ROM area 104 is formed with a wide groove 70 so as to have the same groove shape as the RAM area 105.
If the structure is such that the pit row 60 is recorded in the
The signal values of the AM area 105 and the ROM area 104 (particularly,
The maximum reflectance R _top ) can be easily adjusted. In this case, the groove 70 has a groove depth of 30 to 50 nm so as to have the same groove shape as a guide groove provided in the RAM area 105 described later.
And the groove width is preferably set to 0.40 to 0.60 μm. In particular, the depth of the groove 70 is smaller than the depth of the pre-pit 60 (here, 60 to 100 nm). In addition,
The width of the groove 70 may be narrower or wider than the width of the pre-pit 60.

Further, as shown in FIGS. 7, 8A and 8B, a groove 71 may be provided between each pre-pit row 60. That is, as shown in FIGS. 7, 8A, and 8B, a groove 71 may be provided between the pre-pit rows 60 along the pre-pit row 60. 7 and 8 (a),
In (b), the groove 71 is a groove having a triangular cross section, but may be a groove having a rectangular cross section, for example. Also, groove 7
The depth of 1 is the depth of the pre-pit 60 (here, 60 to 10).
0 nm), but may be deeper than the depth of the pre-pits 60. Further, the width of the groove 71 is narrower than the width of the pre-pit 60, but may be wider than the width of the pre-pit 60.

As described above, the grooves 70,
If the 71 is formed, the RAM area 105 having the guide groove 61 is formed.
Signal value (particularly, maximum reflectance R _topRAM ) and ROM area 1
04 (especially, the maximum reflectance R _topROM ) is easily matched, and the signal value of the ROM area 104 (especially, the maximum reflectance R _topROM ) and the signal value of the RAM area 105 (especially, the maximum reflectance R _topRAM ) Compatibility with is easily obtained.

Here, the ROM area 104 and the RA
If the maximum reflectance R _top is significantly different from that of the M region 105,
From ROM area 104 to RAM area 105 or RAM
If the slice 105 suddenly moves from the area 105 to the ROM area 104, the slice level shifts, and accurate reproduction cannot be performed. Therefore, the grooves 70 and 71 are also formed in the ROM area 104 so that the maximum reflectance R _topROM of the ROM area 104 can be _obtained. To reduce the reflectance difference between the ROM area 104 and the RAM area 105, thereby obtaining the maximum reflectance R of the ROM area 104.
_This makes it easy to match the _topRAM with the maximum reflectance R _topROM of the RAM area 105.

The ROM area 104 and the RAM area 10
Although it is conceivable to increase the maximum reflectance R _topRAM of the RAM area 105 in order to reduce the reflectance difference from
When trying to increase the maximum reflectance R _topRAM of the area 105,
It is necessary to change the groove shape of the RAM area 105, and other groove signals may be out of the proper range, or the groove shape may become unsuitable for changing the unrecorded state to the recorded state. Is not preferred.

Thus, the groove 7 is formed in the ROM area 104.
When 0 and 71 are provided, the pit width Pw is 0.40 to 0.40.
0.70 μm, pit depth Pd is 90 to 150 nm
It is preferred that Note that the ROM area 10
In the case where the grooves 70 and 71 are provided in 4, for example, it is expected that the 11T signal modulation degree m ₁₁ is significantly reduced and the push-pull signal value is increased.

That is, the grooves 70 and 71 are stored in the ROM area 104.
Is formed, the maximum reflectance R of the ROM area 104 is obtained._topROM
Is the maximum reflectance R of the RAM area 105_topRAMAbout the same as
5 and 6 (a) and (b), for example.
Thus, the pit depth P of the pre-pit in the ROM area 104
Since d becomes apparently shallow due to the presence of the groove 70, R_bo
ttom, And the degree of 11T signal modulation is calculated from the following equation.
m₁₁And as a result, the push-pull signal value increases.
It is thought that it becomes easy.

M ₁₁ = (R _top -R _bottom ) / R _top In order to avoid this and increase the 11T signal modulation m ₁₁ , the pit depth Pd must be made deeper than before. In general, when the pit depth Pd is increased, the push-pull signal value is reduced. However, it is considered that the push-pull signal value is somewhat increased by forming the groove as described above. Can be

Here, the RAM area 105 and the RO
A groove is formed in the ROM area 104 in order to make it easier to match the signal value (particularly, the maximum reflectance R _top ) with the M area 104, but the groove is not limited to this. For example, before the actual use, Alternatively, the ROM area 104 may be irradiated with DC (direct current) light (DC light). That is, the DC light beam set to a specific power may be continuously applied to the track at a specific linear velocity.

Normally, in the initialized state, all the recording films are in a crystalline state having a high reflectance. There is a mixed state between the crystalline state of high reflectivity and the amorphous state of low reflectivity. Therefore, by controlling the crystalline state of the recording film by changing the power and linear velocity of the DC light, Can be set arbitrarily to some extent. Therefore, by irradiating the ROM area 104 with DC light so as to obtain a reflectance slightly lower than that of the crystal state in the initialized state, the signal values of the RAM area 105 and the ROM area 104 (particularly, the maximum value) are obtained. The reflectance R _top ) can be easily adjusted.

Incidentally, it is preferable that the pre-pit row 60 in the ROM area 104 be configured to have wobbles. Accordingly, not only a synchronization signal, an address signal, and the like can be obtained from the wobble of the guide groove 61 of the RAM area 105, but also a synchronization signal, an address signal, and the like can be obtained from the wobble in the ROM area 104. Drive is ROM area 104 and RAM area 10
There is no need to switch the detection method of the synchronization signal, the address signal, and the like between 5 and 5, and the drive circuit can be simplified, which is very advantageous.

[0080] normalized wobble signal value NWS _ROM of the pit row 60, as can be reliably reproduced synchronization signal or address signal of the wobble, preferably 0.035 or more 0.060 or less. This is because if the normalized wobble signal value NWS _ROM of the pit row 60 is too small, accurate address information cannot be detected, and if it is too large, the pit row will deviate from the average center of the track. is there.

Normalized wobble signal value NWS_ROMAbout
A description will be given with reference to FIGS. FIG. 9B
Is a pit row 6 having a wobble 90 in the ROM area 104
0, and FIG. 9A shows these wobbles 90.
I obtained from the pit row 60 having ₁-I_TwoIndicates the signal value
ing.

Assuming that the amplitude of the wobble 90 is a, the I ₁ -I ₂ signal value at that time is I _W , which corresponds to a signal value obtained from the wobble 90 (wobble signal value). In FIG. 9A, A is reproduced without tracking,
| I ₁ −I ₂ | after passing through a 5 kHz low-pass filter
This is the peak value of the signal. In actual measurement, 10k
Through a band pass filter of 30 Hz to 30 kHz, and
The peak value of the | I ₁ −I ₂ | signal measured while tracking is used as the wobble signal value I _W of the pit train.

[0083] Thus, the normalized wobble signal value NWS _ROM pit rows 60 is defined by the following equation (6).

[0084]

(Equation 3)

Preferably, the CNR value of the wobble signal of pit row 60 is 26 dB or more. RAM area 1
The normalized wobble signal value NWS of 05 is defined in accordance with the above equation (6), is 0.035 or more and 0.060 or less, and the CNR value of the wobble signal before recording the EFM modulated signal is 35 dB or more; It is preferable that the CNR value of the wobble signal after recording the EFM modulation signal is 26 dB or more.

By the way, the pre-pit array 60 in the ROM area 104 whose main purpose is to reproduce information using diffraction of reflected light, and the groove in the RAM area 105 whose main purpose is tracking control for recording / reproducing. It is considered that the pit 60 and the groove 61 inevitably have a large difference with the (guide groove) 61. In particular, the optimum value of the depth is completely different between the information reproduction purpose and the tracking control purpose.

Therefore, in order to obtain appropriate groove signal characteristics and reproduction signals, the pit shape of the ROM area 104 and the RA
It is expected that the cross-sectional profile of the guide groove shape in the M region 105 is greatly different. In the present embodiment, as shown in FIG. 10, the pre-pits 60 are formed in the ROM area 104, and the guide grooves 61 are formed in the RAM area 105. In addition, in FIG.
Reference numeral 3 denotes a recording mark. Reference numeral 64
The portion other than the recording mark 63 in the groove 61 is also called a land.

Here, the pre-pit row in the ROM area 104
Each of the pits 60 is shown in FIGS. 11 (a) and 11 (b).
As shown in FIG.
The cut width Pw is preferably set to 0.45 to 0.70 μm.
No. In particular, the pit depth Pd should be 70 nm or more.
Is more preferable. As a result, a sufficient 11T signal modulation degree m ₁₁
Is easily obtained. The pit width Pw is 0.50 μ
m or more is more preferable. This ensures that
It becomes easier to obtain a push-pull signal value.

Here, since the 11T signal modulation degree m ₁₁ and the push-pull signal value have a trade-off relationship,
T signal modulation m ₁₁ and the push-pull signal value and has set the pit depth Pd and the pit width Pw as both a preferred value. Further, the groove 61 of the RAM area 105
In consideration of the push-pull signal value, the reflectance, and the like obtained from the AM region 105, the groove depth Gd is set to 30 to 50 nm,
The groove width Gw is preferably set to 0.40 to 0.60 μm. By setting the groove depth Gd and the groove width Gw in this way, a desirable value can be obtained as a push-pull signal value so that accurate tracking can be performed, and the groove shape is damaged when rewriting is repeated. Not to give.

At this time, it is possible to obtain a rewritable compact disc which sufficiently satisfies the groove signal characteristics and reproduction signal characteristics described above. Here, the shape of the groove 61 to be defined is a value measured by optical groove shape measurement. The detailed definition and measurement method are described below. Here, RAM
Since the guide groove 61 in the area 105 is preferably a rectangular shape, it is assumed that the groove shape is a rectangular groove. The method of measuring the intensity of the diffracted light at this time and calculating the width w and the depth d of the groove from the measured values by calculation will be described below.

As shown in FIG. 12, a He-Cd laser
A laser beam 2 with a groove on one side
The carbonate substrate 3 is arranged vertically and has no groove.
Irradiate the laser beam 2 from the surface. Polycarbonate
Of each diffracted light from the groove of the substrate 3, ie, the intensity of the zero-order light
I₀, Primary light intensity I₁, I_-1, Secondary light intensity I_Two, I_{- Two}
Is measured with a photodetector.

At this time, the relationship of the following equations (7) and (8) is established. The width w and the depth d are obtained by simultaneously solving the equations (7) and (8). The actual shape of the groove 61 is not always an accurate rectangle, but in the present embodiment, a value in which the width w and the depth d of the groove 61 are uniquely determined by the above measurement method is used.

[0093]

(Equation 4)

The width and depth of the pit 60 were determined by an atomic force microscope (AFM) so that the radius of curvature at the tip was 10 nm.
Are measured using the probe of No. 1. A preferred example of a method for forming the grooves 61 and the pits 60 having such shapes will be described below. Usually, the following steps are performed to manufacture an optical disc. In other words, a photosensitive layer is formed by applying a photosensitive resin on a clean and flat glass plate that has been polished, and a laser beam finely focused by an objective lens moves in the radial direction of the master while rotating the glass plate. While moving the master or the optical system, the photosensitive layer is irradiated to expose a desired pattern. It is developed using an alkali developing solution to remove the exposed portions to form a master master having a preformat of a concavo-convex pattern.

According to the above manufacturing method, there are roughly two types of profiles of the cross-sectional shape of the pit 60 or the guide groove 61. That is, a rectangular shape is formed by exposing the exposed portion with a large power that reaches the glass master, and a triangular or Gaussian shape is formed by exposing the exposed portion with a power that stops halfway through the resist film. Sometimes it becomes a groove.

The cross-sectional profile of the laser beam applied to the resist film is a Gaussian-shaped groove, and if the optical system and the resist film to be used are constant, the groove width is uniquely determined if the groove depth is determined. Is done. That is, the groove width becomes narrower as the groove depth decreases, and the groove width increases as the groove depth increases. However,
The guide groove 61 formed in the RAM area 105 of the optical disc 100 of the present embodiment is a guide groove having a substantially rectangular shape, and the groove shape is as shallow as the groove depth Gd of 30 to 50 nm.
It is preferable that the groove width Gw is as wide as 0.40 to 0.60 μm. In a normal manufacturing method, the guide groove 61 having the above groove shape is used.
Is difficult to produce.

If the laser wavelength is lengthened or an objective lens having a small numerical aperture is used, the guide groove 61 having the above-mentioned groove shape can be manufactured, but it is not easy to form the exposed portion with high contrast. Absent. Therefore, in manufacturing a rewritable compact disc having a guide groove having the above-mentioned groove shape, it is preferable to use the following manufacturing method.

That is, according to the pre-pit rows and grooves to be formed on the resist film 81 formed on the glass substrate 80, the master master on which the pre-pit rows and grooves have been formed by irradiating and irradiating with a laser beam L and developing. Manufacturing method of forming a stamper based on the master master, forming a substrate 50 provided with the pre-pit rows 60 and grooves 61 based on the stamper, and then providing a phase-change recording layer 52 In irradiating the resist film 81 with the laser beam L in accordance with the groove, as shown in FIG. 14, a plurality of laser beams L1 and L2 are
The laser beams L1 and L2 are arranged so as to partially overlap in the vertical direction with respect to the traveling direction, and are irradiated and exposed (exposure method 1).

Alternatively, according to the pre-pit rows and grooves to be formed on the resist film 81 formed on the glass substrate 80, a laser beam is irradiated and exposed to light and developed to produce a master master having the pre-pit rows and grooves formed thereon. Then, a stamper is formed on the basis of the master master, and the substrate 5 on which the pre-pit row 60 and the groove 61 are provided based on the stamper.
In the manufacturing method in which the phase change recording layer 52 is formed after the formation of the laser beam L3, when the resist film 81 is irradiated with the laser beam L according to the groove 61, as shown in FIG. 2.5 × 10 ⁶ perpendicular to the direction
The resist film 81 is exposed by irradiating while vibrating at a frequency of not less than 25 times / m and not more than 25 × 10 ⁶ times / m (exposure method 2).

Hereinafter, the exposure methods 1 and 2 will be described in more detail. (Exposure Method 1) FIG. 13 shows an example of an exposure apparatus used in the main exposure method. In FIG. 13, reference numeral 9 denotes a laser generator, reference numerals 11, 18, 23, and 24 denote beam splitters,
5, 20, 21 are reflecting mirrors, 14, 17 are optical modulators, 18
Is an optical polarizer, 25 is an objective lens, and 26 is a glass substrate coated with a photoresist film. As the laser light, an Ar wavelength of 488 nm, a Kr wavelength of 413 nm, or the like is used.

A laser beam 10 emitted from a laser generator is split into two laser beams 12 and 13 by a beam splitter 11. After the laser beams 12 and 13 are intensity-modulated by the optical modulators 14 and 17, respectively, the laser beam 12 is wobbled by the optical polarizer 16 so that the guide groove represents the address information FM-modulated at the center frequency of 22.05 KHz. Angle polarized to have

The laser beam 12 is split by the beam splitter 18 into laser beams 19 and 22.
Thereafter, the three laser beams 13, 19, and 22 are aligned on the glass substrate in the radial direction of the substrate by the reflecting mirror 20 and the beam splitters 23 and 24, and the laser beams 19 and 22 are formed by the laser beams. The parts are arranged so as to overlap each other, and the laser beam 13 is arranged so as to be at the center of the laser beams 19 and 22, and enters the objective lens 25.

A glass substrate 26 coated with a 900 ° -thick photoresist film is rotated at a linear velocity of 1.2 m / s, and the laser beams 13, 19 and 22 emitted from the objective lens 25 are irradiated thereon. Then, the photoresist film is exposed. The pits 60 or grooves (grooves) 6 are subjected to a developing process using an alkaline developer.
1 can be formed.

When exposing a normal pit row, a laser beam 13 is irradiated with a laser power such that the exposed portion reaches the glass substrate, and the photoresist film is exposed to form a rectangular exposed portion. . On the other hand, during the exposure of the RAM area 105, when the beams 19 and 22 are irradiated,
The photoresist film is exposed to form an exposed portion. At this time, the amount of laser light incident on the objective lens is not large enough to expose the photoresist film up to the glass substrate,
As shown in FIG. 14, a plurality of laser beams L1, L2
Between adjacent laser beams,
By adjusting the position and the intensity ratio of the two beam spots BS while partially overlapping in the direction perpendicular to the traveling direction of L2, the shape is closer to a rectangular shape than in the case of single-beam exposure. The shape of the groove can be obtained.

When exposing the pit row 60 having the wobbles 90, an optical deflector (not shown) is added after the light modulator 17, and the laser beam 13 is applied to the pit row 6 to be formed.
The light is angle-polarized so that 0 has a wobble 90 representing address information FM-modulated at a center frequency of 22.05 KHz. When the pit row 60 having the wobbles 90 is connected by a shallow groove, the beams 19 and 22 are angularly polarized according to the wobble 90 and irradiated to form a groove. At the same time, the intensity of the beam 13 is modulated by a pit signal. Irradiation may form a pit portion.

Alternatively, the beams 19 and 22 are
It is also possible to irradiate with intensity modulated by a pit signal while irradiating with the angle polarized light to zero, thereby exposing only the pit 60 part deeply. (Exposure Method 2) This exposure method 2 will be described with reference to FIG. 13 used for describing the above-described exposure method 1.

First, the laser beam 10 emitted from the laser generator 9 is split by the beam splitter 11 into two laser beams 12 and 13. As laser light, Ar wavelength 488 nm, Kr wavelength 413
nm or the like is used. The laser beams 12 and 13 are intensity-modulated by the optical modulators 14 and 17, respectively, and thereafter, only the laser beam 12 is modulated by the optical polarizer 16.
At a high frequency of 5 MHz, it is polarized at an angle of 10 mrad, and at the same time, the guide groove formed thereby has a center frequency of 2 mrad.
It is angle-polarized so as to have a wobble that represents address information FM-modulated at 2.05 KHz.

The laser beam 12 is split into laser beams 19 and 22 by the beam splitter 18. The laser beam 19 is blocked by a shield plate (not shown) so that only the laser beam 22 passes through the beam splitter 23. After that, laser beam 1
3 and the laser beam 22 are arranged by a beam splitter 24 so as to overlap at the same position on the glass substrate, and enter the objective lens 25.

A glass substrate 26 coated with a 900 ° thick photoresist film is rotated at a linear velocity of 1.2 m / s, and a laser beam 1 emitted from an objective lens is placed thereon.
When irradiating 3, 22 the photoresist film is exposed. The pits 60 or the grooves (grooves) 61 can be formed by subjecting this to a developing treatment with an alkaline developing solution.

When exposing a normal pit row, a laser beam 13 is irradiated with a laser power such that the exposed portion reaches the glass substrate, and the photoresist film is exposed to form a rectangular exposed portion. . On the other hand, when the RAM area 105 is exposed, the angle-polarized laser beam 2
Irradiation 2 exposes the photoresist film to form an exposed portion. At this time, the amount of laser light incident on the objective lens is not large enough to expose the photoresist film onto the glass substrate and is exposed only halfway through the resist film. However, since the laser beam is angularly polarized at a high frequency of 5 MHz, it is angularly polarized. A groove shape closer to a rectangular shape can be obtained as compared with the case of exposing with a beam that has not been subjected to the above.

As shown in FIG. 15, at least 2.5 × 10 ⁶ times / m in the direction perpendicular to the traveling direction of the laser beam L3.
It is preferable to expose the resist film 81 by irradiating while oscillating at 25 × 10 ⁶ times / m or less. For example, linear velocity 1.
A substrate rotating at 2 m / s is subjected to angular polarization at a high frequency of 3 to 30 MHz. If the linear velocity is 2.4 m / s, the light is angularly polarized at a high frequency of 6 to 60 MHz.

When exposing the pit row 60 having the wobbles 90, an optical deflector (not shown) is added after the optical modulator 17, and the laser beam 13 is applied to the pit row 6 to be formed.
The light is angle-polarized so that 0 has a wobble 90 representing address information FM-modulated at a center frequency of 22.05 KHz. When the pit row 60 having the wobbles 90 is connected by a shallow groove, the beams 19 and 22 are angularly polarized according to the wobble 90 and irradiated to form a groove. At the same time, the intensity of the beam 13 is modulated by a pit signal. Irradiation may form pits 60.

Alternatively, the beams 19 and 22 are
It is also possible to irradiate with intensity modulated by a pit signal while irradiating with the angle polarized light to zero, thereby exposing only the pit 60 part deeply. The exposed glass substrate obtained by the above-mentioned exposure method 1 and exposure method 2 is developed using an alkali developing solution to remove the exposed portion, thereby forming a master having a concave / convex pattern preformat. A nickel thin film is formed on the surface of the master by sputtering or the like, and a wet stamp is applied in an electrolytic solution containing nickel ions to form a stamper on the surface of the master master for an optical disk, and the nickel stamper is peeled off from the master. Then, a stamper on which the preformat information of the master is transcribed in reverse is obtained.

The pre-pit row 60
After forming the substrate 50 provided with the groove 61 and the groove 61, the rewritable compact disc 100 of the present invention can be obtained by providing a layer including the phase-change recording layer 52. next,
The physical configuration of the rewritable compact disc of the present invention will be described. As shown in FIG. 2, at least a phase change type recording layer 52 is provided on the substrate 50. Preferably, protective layers 51 and 53 are provided above and below the recording layer 52, and a reflection layer 54 is provided.

As the disk substrate 50, a substrate transparent to recording / reproducing light, such as a resin such as polycarbonate, acrylic, or polyolefin, or glass is used.
When the protective layers 51 and 53 are provided above and below the recording layer 52,
The thickness of the protective layer is desirably about 10 nm to 500 nm.
Materials for the protective layers 51 and 53 include a refractive index, a thermal conductivity,
It is determined in consideration of chemical stability, mechanical strength, adhesion, etc., but it is highly transparent and has a high melting point, such as oxides, sulfides, nitrides of metals and semiconductors, and fluorine such as Ca, Mg, and Li. Can be used. These oxides, sulfides, nitrides, and fluorides do not always need to have a stoichiometric composition, and it is also effective to control the composition for controlling the refractive index and the like, or to use a mixture. In particular, a dielectric mixture is preferable in consideration of the repetitive recording characteristics. Therefore, the protective layer 5
1, 53 is also called a dielectric layer.

More specifically, a mixture of ZnS, TaS ₂ , a rare earth sulfide and a heat-resistant compound such as an oxide, a nitride, a carbide, and a fluoride can be used. For example, ZnS and SiO
₂ , ZnS and rare earth oxide, ZnS and ZnO, ZnS-
Mixtures of SiO ₂ —TaO _x , ZnS—ZnO—SiO ₂ , and the like are preferred. Considering the repetitive recording characteristics, it is desirable that the film density of these protective layers be 80% or more of the bulk state from the viewpoint of mechanical strength. When a mixture dielectric thin film is used, the theoretical density of the following equation is used as the bulk density.

Ρ = Σmiρi (9) mi: molar concentration of each component i ρi: single bulk density If the thickness of the protective layers (dielectric layers) 51 and 53 is less than 10 nm, the substrate 50 and the recording film 52 Tend to have an insufficient effect of preventing deformation of the layer and do not serve as a protective layer. On the other hand, the thickness of the protective layers (dielectric layers) 51 and 53 is 500 nm.
When the value exceeds, the internal stress of the dielectric itself and the difference in elastic characteristics with the substrate become remarkable, and cracks are easily generated.

In particular, the protective layer (lower protective layer) 51 inserted between the substrate 50 and the recording layer 52 needs to suppress substrate deformation due to heat, and is preferably 50 nm or more. 50n
If it is less than m, microscopic substrate deformation will accumulate during repeated overwriting, and the reproduction light will be scattered, resulting in a significant increase in noise. The lower protective layer 51 has a thickness of 200
Although the upper limit is substantially about nm, it is not preferable that the thickness is larger than 200 nm because the groove shape on the recording layer 52 greatly changes from the groove shape on the substrate 50. That is, the groove depth becomes shallower than the intended shape on the substrate surface, and the groove width becomes smaller than the intended shape on the substrate surface, which is not preferable. More preferably, it is 150 nm or less.

On the other hand, the protective layer (upper protective layer) 53 inserted between the recording layer 52 and the reflective layer 54 needs to be at least 10 nm in order to suppress deformation of the recording layer 54.
On the other hand, if the thickness is more than 50 nm, microscopic plastic deformation is likely to be accumulated in the upper protective layer 53 repeatedly during overwriting, which undesirably scatters reproduction light and increases noise. According to the experiment, the thinner the thickness of the upper protective layer 53 is in the range of 10 to 50 nm, the smaller the deterioration during repeated overwriting becomes.

At the time of recording at a relatively low linear velocity, if importance is placed on repeated overwrite durability, the upper protective layer 53 may be used.
Is preferably less than 30 nm. In addition, when recording at a high linear velocity, it is necessary to perform recording with short-time laser irradiation. Therefore, it is preferable to increase the recording sensitivity, and it is effective to increase the thickness of the protective layer relatively. . For example, when recording at a linear velocity of 9 m / s or more, the thickness of the upper protective layer is preferably about 25 to 50 nm.

In order to widen the usable linear velocity range even when the recording linear velocity is low, it is effective to increase the thickness of the reflective layer 54. In this case, however, the recording sensitivity is deteriorated, and In some cases, it is effective to increase the thickness of the upper protective layer 53 as in the case of (1). At this time, the thickness of the upper protective layer 53 is preferably about 25 to 50 nm. Various conventionally known materials can be used as the material of the phase-change recording layer 52, such as GeSbTe, InSbTe, AgSbTe, and ASbTe.
gInSbTe, AgGeSbTe, InGeSbTe
Sb ₇₀ Te _30, which is stable in both crystalline and amorphous states and capable of high-speed phase transition between the two states.
An alloy mainly containing an SbTe alloy near the eutectic point is most preferable. This is because segregation hardly occurs when repeated overwriting is performed, and this is the most practical material.

A particularly preferred composition of the phase change type recording layer 52 is a Ma _w (Sb _z Te _{1 -z} ) _{1 -w} alloy (where 0 ≦ w ≦
0.3, 0.5 ≦ z ≦ 0.9, Ma is In, Ga, Z
n, Ge, Sn, Si, Cu, Au, Ag, Pd, P
t, Pb, Cr, Co, O, N, S, Se, Ta, N
b, V, Bi, Zr, Ti, Mn, Mo, Rh and at least one selected from rare earth elements). More preferably, 0 ≦ w ≦ 0.2, and 0.6 ≦ z ≦ 0.8.
It is.

According to the study of the present inventors, the linear velocity dependency is determined by the main components Sb and Te, and Sb ₇₀ Te
_{In the} vicinity of the ₃₀ eutectic point, the crystallization rate tends to increase as the Sb / Te ratio increases. Ge or I near this eutectic composition
ternary material with the addition of n in repetitive overwriting in a specific recording pulse pattern, are widely known _{GeTe-Sb 2 Te 3, InTe} -Sb 2 Te 3
Deterioration is less than that of the material near the pseudo binary alloy, or the jitter of the mark edge when the mark length is recorded is small,
Excellent material. Further, the crystallization temperature is high and the stability over time is excellent.

Since the recording layer 52 is usually amorphous immediately after film formation, the entire recording layer is crystallized to be in an initialized state (unrecorded state) as described later. According to this composition, the CD linear velocity is at least one time speed (1.2 to 1.4 m).
/ S) to 24x speed (28.8 m / s to 33.6 m /
s) Good overwriting can be performed over a wide range of linear velocities.

As a more preferred example, Mbα ₁ Inβ ₁
Sbγ ₁ Teη ₁ (However, 0.03 ≦ α1 ≦ 0.1,
0.03 ≦ β1 ≦ 0.08, 0.55 ≦ γ1 ≦ 0.6
5, 0.25 ≦ η1 ≦ 0.35, 0.06 ≦ α1 + β1
≦ 0.13, α1 + β1 + γ1 + η1 = 1, Mb is Ag
Or at least one of Zn). More preferably, in the above composition, 0.03 ≦ α1 ≦
0.1, 0.05 ≦ β1 ≦ 0.08, 0.6 ≦ γ1 ≦
0.65, 0.25 ≦ η1 ≦ 0.30, 0.06 ≦ α1
+ Β1 ≦ 0.13, α1 + β1 + γ1 + η1 = 1.

In this composition range, a sufficient erasing ratio can be obtained at the time of overwriting up to about 10 m / s. Further, it can be used as a composition having excellent stability over time. In has the effect of increasing the crystallization temperature and increasing the stability over time. In order to ensure the storage stability at room temperature, In is preferably added at 3 atomic% or more. Separation is likely to occur, and segregation is likely to occur due to repeated overwriting. More preferably, it is 5 atomic% or more and 8 atomic% or less.

Ag or Zn facilitates initialization of the amorphous film immediately after film formation. Although it depends on the initialization method, addition of 10 atomic% or less is sufficient, and if it is too much, stability over time is rather deteriorated, which is not preferable. On the other hand, if the total of Ag or Zn and In exceeds 13 atomic%, segregation is apt to occur during repeated overwriting, which is not preferable.

As another example of a suitable recording layer 52, Mc _v
Ge _y (Sb _x Te _1-x ) _1-yv (where 0.6 ≦ x ≦
0.8, 0.01 ≦ y ≦ 0.15, 0 ≦ v ≦ 0.15,
0.02 ≦ y + v ≦ 0.2, and Mc is at least one of Ag and Zn). According to this composition, the low melting point metal I in the aforementioned MbInSbTe alloy
It is possible to improve the ease of precipitation of the n- and indium alloys.

However, on the other hand, the time required for the initialization process rapidly increases with the addition of Ge. In order to overcome both the easiness of precipitation of In and the difficulty of initialization by Ge, Mdα ₂ Inβ ₂ Geδ ₂ Sbγ ₂ Teη ₂ (where 0 ≦ α2 ≦ 0.1, 0.001 ≦ β2 ≦ 0 .1,
0.01 ≦ δ2 ≦ 0.1, 0.5 ≦ γ2 ≦ 0.8, 0.
15 ≦ η2 ≦ 0.4, 0.03 ≦ β2 + δ2 ≦ 0.1
5, a composition of α2 + β2 + δ2 + γ2 + η2 = 1 and Md is at least one of Ag and Zn) may be used.

The recording layer 52 has a thickness of 10 nm to 30 nm.
Is preferable. If the thickness of the recording layer 52 is less than 10 nm, it is difficult to obtain a sufficient contrast between the reflectance in the crystalline state and the amorphous state, and the crystallization speed tends to be slow. Cheap. 30
If it exceeds nm, optical contrast is still difficult to obtain, and cracks tend to occur, which is not preferable.

When the thickness is less than 10 nm, the reflectance is too low, and when the thickness is more than 30 nm, the heat capacity is increased and the recording sensitivity is apt to deteriorate. Furthermore, when the film thickness of the recording layer 52 is 3
If the thickness is larger than 0 nm, the volume change due to the phase change is remarkable, and the recording layer 52 itself and the upper and lower protective layers 51 and 53 are remarkably affected by the repetitive volume change due to repetitive overwriting, resulting in microscopic and irreversible deformation. Accumulates and easily becomes noise. As a result, repeated overwrite durability is reduced. In a high-density recording medium such as a rewritable DVD (rewritable compact disc), the requirement for noise is more severe.
m or less.

The recording layer 52 is often obtained by subjecting an alloy target to DC (direct current) or RF (high frequency) sputtering in an inert gas, particularly Ar gas. The density of the recording layer 52 is desirably 80% or more, more preferably 90% or more of the bulk density. The bulk density as used herein can be measured by, of course, preparing an alloy lump. In the above equation (9), the molar concentration of each component is set to atomic% of each element, and the bulk density is set to each element. May be used instead of the approximate molecular weight.

In the sputter deposition method, the density of the recording layer 52 is reduced by lowering the pressure of a sputter gas (a rare gas such as Ar) at the time of deposition, or by disposing a substrate close to the front of the target. It is necessary to increase the amount of high-energy Ar applied to the layer 52. High-energy Ar means that Ar ions irradiated to the target for sputtering are partially rebounded and reach the substrate side, or Ar ions in the plasma are accelerated by the sheath voltage on the entire surface of the substrate and reach the substrate. Is one of Atomic peening effect (at
omic peening effect).

In sputtering using Ar gas, which is generally used, Ar is mixed into a sputtered film by an atomic peening effect. A in the membrane
atomic peening effect (atomic peeni
ng effect) can be estimated. That is, if the amount of Ar is small, it means that the high-energy Ar irradiation effect is small, and a film having a low density is easily formed. On the other hand, Ar
If the amount is large, high energy Ar irradiation is intense and the density becomes high, but Ar taken in the film repeatedly precipitates as voids during overwriting and deteriorates the durability of repetition.

An appropriate amount of Ar in the recording layer film is 0.1 atomic% or more and less than 1.5 atomic%. Further, it is preferable to use high-frequency sputtering rather than DC sputtering because the amount of Ar in the film is reduced and a high-density film can be obtained. The reflective layer 54 is preferably made of a material having a high reflectivity. In the present invention, the heat conductivity is particularly high even through the upper dielectric layer.
A high-reflectivity metal such as Au, Ag, or Al, which can be expected to have a heat radiation effect, or an alloy containing this as a main component is used. In order to control the thermal conductivity of the reflective layer itself and improve corrosion resistance, Ta,
Ti, Cr, Mo, Mg, V, Nb, Zr, Mn, Si
An alloy containing a small amount of, for example, 15 at% or less is preferable. In particular, an alloy of Al1-z Taz (0 <z ≦ 0.15) has excellent corrosion resistance and is effective in improving the reliability of the present optical information recording medium.

The thickness of the reflective layer 54 is preferably 50 nm or more in order to completely reflect incident light without transmitted light. When the thickness is more than 500 nm, the heat radiation effect is not changed and the productivity is unnecessarily deteriorated, and cracks are easily generated. In particular, when the thickness of the upper protective layer 53 is 40 nm or more and 50 nm or less, the amount of impurities contained is set to less than 2 atomic% in order to make the reflective layer 54 have high thermal conductivity.

The recording layer 52 and the protective layers 51 and 5 described above.
3. The reflection layer 54 is formed by a sputtering method or the like. It is desirable to form a film using an in-line apparatus in which a target for a recording layer, a target for a protective layer, and if necessary, a target for a reflective layer material are installed in the same vacuum chamber, in order to prevent oxidation and contamination between layers. It is also excellent in productivity.

Next, a method for initializing the optical information recording medium of the present invention will be described. The recording layer 52 of the optical information recording medium of the present invention has an as-deposited state (as-depos state).
(it state; state immediately after film formation) is amorphous, so that the entire surface of the disk needs to be crystallized in a short time in order to make the initial state a crystalline state. This step is called initial crystallization. Usually, this initial crystallization is performed by irradiating a rotating disk with a laser beam focused to several tens to hundreds of microns.

In particular, melting initialization is effective for shortening the time required for initialization and for surely performing initialization with one light beam irradiation. It should be noted that as long as the protective layer 51, 53 has a sandwich structure, the melting does not mean that the recording medium is immediately destroyed. For example, a light beam (gas or semiconductor laser light) focused to a diameter of about 10 to several hundreds μm or an elliptical light beam focused to a major axis of 50 to several hundreds μm and a short axis of about 1 to 10 μm is used locally. The recording medium is not destroyed if it is heated to a low temperature and melted only at the center of the beam. In addition, the heating of the peripheral portion of the beam causes the molten portion to be preheated, so that the cooling rate is reduced, and favorable recrystallization is performed. Using this method, for example, one-tenth of conventional solid-phase crystallization
In addition, the initialization time can be shortened, the productivity can be significantly shortened, and a change in crystallinity at the time of erasing after overwriting can be prevented.

[0140]

Hereinafter, the present invention will be described with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist. Example 1 A master master for an optical disk was manufactured by using the above-described exposure methods 1 and 2. That is, a diameter of 46 to 54 m
m is a ROM area, and has a depth of 80 n having address information by a wobble 90 according to the Orange Book standard.
m, a prepit having a width of 0.60 μm, and a diameter of 54 to 1
A range of 16 mm is a RAM area, and a depth of 40 n having address information by wobble according to the Orange Book standard
m, and a guide groove having a width of 0.550 μm was provided. The pre-pit row and the guide groove are spirally connected to one another, and the track pitch is 1.6 μm.

In the exposure method 1, the Kr wavelength of 413 nm was used as the laser beam in the exposure apparatus shown in FIG.
Was irradiated on a substrate rotating at a linear velocity of 1.2 m / s through an objective lens having a numerical aperture of NA 0.90. The pit forming beam 13 has a diameter of about 0.26 μm, and the groove forming beams 19 and 22 each have a diameter of about 0.3 μm.
The distance between the beam and the beam 22 was 0.2 μm.

In the exposure method 2, in the exposure apparatus shown in FIG. 13, a laser beam having a wavelength of 413 nm of Kr is used to irradiate a substrate rotating at a linear velocity of 1.2 m / s through an objective lens having a numerical aperture of NA 0.90. did. The pit forming beam 13 has a diameter of about 0.26 μm and the groove forming beam 2
2 is about 0.3 μm in diameter and the beam 22 is 10 mrad
At 5 MHz.

A stamper was prepared using the master master for optical disks produced by the above method, and a disk substrate having a diameter of 120 mm was prepared by injection molding polycarbonate. The molding was performed under the following conditions using a disc molding machine MO40DH manufactured by Nissei Plastic Industry Co., Ltd. That is, resin temperature 350 ° C., stamper side (fixed side) mold temperature 112 ° C., movable mold temperature 107 ° C., spool temperature 1
00 ° C, cut punch temperature 105 ° C, filling speed 80
Millisecond, clamping force 36 tons, cooling time 6.8 seconds.

On this substrate, a protective layer made of (ZnS) ₈₀ (SiO ₂ ) ₂₀ and having a thickness of 110 nm and Ag ₅ In ₅ Sb _60.5 T
e, a recording layer having a thickness of 16 nm made of _29.5 and (ZnS)
₈₅ (SiO ₂ ) ₁₅ 44 nm thick protective layer and Al
A reflective film of _99.5 Ta _{0.5 having} a thickness of 222 nm was sequentially formed in a clean vacuum chamber evacuated to a high vacuum. Finally,
In order to prevent deformation of the recording medium, an ultraviolet curable resin was formed to a thickness of several μm.

The optical recording medium was subjected to a read power of 0.8 mW and a linear velocity of 1.2 m / s using an objective lens having a NA of 0.50 and a laser having a wavelength of 780 nm. Various evaluations were made of the groove signal characteristics of the RAM region and the reproduction signal characteristics of the ROM region and the RAM region after recording. In the RAM area, N
Using an objective lens of A0.50 and a laser having a wavelength of 780 nm, a random pattern of an EFM modulation signal was recorded under the conditions of a recording power of 13 mW and a linear velocity of 2.4 m / s, and evaluated as a RAM area after recording.

Table 1 shows the ROM area, before and after recording.
Push-pull signal value (PP) of RAM area, radial
Contrast value (RC), CNR value of wobble signal (W
CNR), normalized wobble signal value (NWS), maximum reflection
Rate R_top(%), 11T signal modulation degree m of the EFM modulation signal
₁₁(M) and an asymmetry value (Asym). here
, ROM area, push-pull signal before and after recording
The value PP is a ROM standardized by the maximum signal level, respectively.
Area push-pull signal value | I₁-I_Two|_{RO M}/
I_topROM, Recording standardized by groove signal level in RAM area
Previous push-pull signal value | I₁-I_Two| / I_g, RAM area
Push-pull after recording normalized by the maximum signal level of the area
Signal value | I₁-I_Two|_a/ I_topRAMSay.

Table 2 shows the ROM area and the RAM before recording.
The ratio of the push-pull signal value of the area and the ratio of the maximum reflectance are shown. In addition, the evaluation results of the optical disks manufactured using the optical disk masters manufactured by the exposure method 1 and the exposure method 2 are described.

[0148]

[Table 1]

[0149]

[Table 2]

The 3T signal modulation degree in the ROM area 104
m_ThreeAnd 11T signal modulation m₁₁And the ratio (m_Three/ M₁₁)_ROMIs
0.56. In addition, R after recording by exposure method 1
3T signal modulation degree m of AM area 105_ThreeAnd 11T signal modulation
Degree m₁₁And the ratio (m_Three/ M₁₁)_{RA M}Was 0.55. Sa
Further, 3 of the RAM area 105 after recording by the exposure method 2
T signal modulation degree m_ThreeAnd 11T signal modulation m₁₁And the ratio (m_Three/
m₁₁)_RAMWas 0.55. (Comparative Example 1) In Comparative Example 1, the ROM area 104
The cut depth Pd is 129 nm and the width is 0.52 μm.
The pit 60 was deeper than that of the first embodiment. In addition, RAM
The region 105 was the same as in the first embodiment.

At this time, the program after recording in the RAM area 105 is
Push-pull signal value in ROM area 104
Ratio to signal value | I₁-I_Two|_a/ | I₁-I_Two|_ROMIs 175
/39=4.49. Thus, the above-described embodiment
, The push-pull signal after recording in the RAM area 105
Ratio between signal value and push-pull signal value in ROM area 104 |
I₁-I_Two|_a/ | I₁-I_Two|_ROMPreferred range as
0.78 or more and 1.3 or less.
Further, the 11T signal modulation degree m in the ROM area 104 ₁₁Is
0.84 (m₁₁= 0.84). Furthermore, ROM
The radial contrast value RC of the region 104 is 0.48
(RC = 0.48).

As a result, tracking was lost at the switching point between the RAM area 105 and the ROM area 104. Comparative Example 2 In Comparative Example 2, the pit depth Pd of the ROM area 104 was 107 nm, and the pit width Pw was 0.42 μm.
m, the pit 60 was made deeper and the pit width Pw was made narrower than in the first embodiment. The RAM area 105 was the same as in the first embodiment. Here, since the push-pull signal value of the ROM area 104 in Comparative Example 1 was small, the pit width Pw was narrowed to increase it.

At this time, the ratio | I ₁ −I ₂ | _a / | I ₁ −I ₂ | _ROM of the push-pull signal value after recording in the RAM area 105 and the push-pull signal value in the ROM area 104 is 175.
/79=2.22. Thus, in the above-described embodiment, the ratio between the push-pull signal value after recording in the RAM area 105 and the push-pull signal value in the ROM area 104 |
I ₁ −I ₂ | _a / | I ₁ −I ₂ | The range from 0.78 to 1.3, which is a preferable range for the _ROM , is still largely out of the range. The 11T signal modulation degree m ₁₁ of the ROM area 104 was 0.81 (m ₁₁ = 0.81). Furthermore, the radial contrast value RC of the ROM area 104
Was 0.43 (RC = 0.43).

As a result, tracking was lost at the switching point between the RAM area 105 and the ROM area 104. (Embodiment 2) In this embodiment 2, the pit depth Pd of the ROM area 104 is 57 nm, and the pit width Pw is 0.56 μm.
The pits were made shallower than in Example 1 described above. In addition,
The RAM area 105 was the same as in the first embodiment.

At this time, the ratio | I ₁ −I ₂ | _a / | I ₁ −I ₂ | _ROM of the push-pull signal value after recording in the RAM area 105 and the push-pull signal value in the ROM area 104 is 175.
/181=0.97. As described above, in the above embodiment, the ratio | I ₁ −I ₂ | _a / | I ₁ −I ₂ | _ROM of the push-pull signal value after recording in the RAM area 105 and the push-pull signal value in the ROM area 104 is used. It was within the preferred range of 0.78 to 1.3. For this reason, tracking did not deviate at the switching point between the RAM area 105 and the ROM area 104.

However, the 11T signal change in the ROM area 104
Furnishing m₁₁Was 0.40 (m ₁₁= 0.40). This
11T signal modulation degree m₁₁Is small, so
The correct pattern cannot be read and good playback cannot be performed.
Was. Furthermore, the radial contrast of the ROM area 104
The value RC was 0.17 (RC = 0.17). this
Since the radial contrast value RC is also small,
It is difficult to count and seek cannot be performed normally
Was. (Comparative Example 3) In Comparative Example 3, the groove of the RAM area 105 was
The depth Gd is 24 nm and the groove width Gw is 0.38 μm.
The groove 61 is made shallower and the groove width Gw is made narrower than in the first embodiment described above.
Was. The ROM area 104 is described in the above embodiment.
Same as 1 The recording power is 10.3 mW.
did.

At this time, the ratio | I ₁ −I ₂ | / | I ₁ −I ₂ | _a of the push-pull signal value before recording in the RAM area 105 and the push-pull signal value after recording in the RAM area 105 is 1 .5
It was 6. Also, the ratio | I ₁ −I ₂ | _a / | I ₁ −I ₂ | _ROM of the push-pull signal value after recording in the RAM area 105 and the push-pull signal value in the ROM area is 488/177 =
It was 2.76. As described above, in the above-described embodiment, the push-pull signal value and the R
Ratio to push-pull signal value of OM region 104 | I ₁ −I ₂
| _A / | went wide preferred 0.78 to 1.3 range is set to range as _ROM | I ₁ -I _2. For this reason, tracking was lost at the switching point between the RAM area 105 and the ROM area 104.

The 11T signal modulation degree m ₁₁ in the RAM area 105 was 0.54 (m ₁₁ = 0.54). For such small is 11T signal degree of modulation m _11, even when reproducing only the RAM area 105 not read the exact pattern of the signals could not favorable reproduction. Further, the radial contrast value RC of the RAM area 105 was 0.37 (RC = 0.37). The maximum reflectance R _topRAM of the RAM area 105 is 20.8% (R _top = 20.8
%), The maximum reflectance R _topROM of the ROM area 104 is 22.
9% (R _topRAM = 22.9%). Therefore, R
_topROM / R _topRAM = 22.9 / 20.8 = 1.10. (Comparative Example 4) In Comparative Example 4, the groove depth Gd of the RAM area 105 was set to 74 nm, the groove width Gw was set to 0.48 μm, and the groove 61 was made deeper than in the first embodiment. Note that the ROM area 104 was the same as in the first embodiment. The recording power was 12 mW.

At this time, the ratio | I ₁ −I ₂ | / | I ₁ −I ₂ | _a of the push-pull signal value before recording in the RAM area 105 and the push-pull signal value after recording in the RAM area 105 is 2 .4
It was one. Also, the ratio | I ₁ −I ₂ | _a / | I ₁ −I ₂ | _ROM of the push-pull signal value after recording in the RAM area 105 and the push-pull signal value in the ROM area is 693/177 =
It was 3.92. As described above, in the above-described embodiment, the push-pull signal value and the R
Ratio to push-pull signal value of OM region 104 | I ₁ −I ₂
| _A / | went wide preferred 0.78 to 1.3 range is set to range as _ROM | I ₁ -I _2. For this reason, tracking was lost at the switching point between the RAM area 105 and the ROM area 104.

The 11T signal modulation degree m ₁₁ of the RAM area 105 was 0.67 (m ₁₁ = 0.67). Further, the maximum reflectance R _topRAM of the RAM area 105 is 13.3.
% (R _top = 13.3%), and the maximum reflectance R _topROM of the ROM area 104 was 22.9% (R _topRAM = 22.9%). Therefore, R _topROM / R _topRAM = 22.9 / 1
3.3 = 1.72.

As described above, R _topROM and R _topRAM are used in both areas.
Therefore, it took a long time to adjust the gain, and it was difficult to continuously reproduce both areas.

[0162]

According to the present invention, it is possible to provide a highly compatible rewritable optical disk having a RAM area and a ROM area on one medium surface. As a result, one CD-RW
The use of application software and the like and the recording of data can be performed simultaneously by the writer, and its use value is extremely high.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an arrangement of a non-data area and a data area of a CD-RW as a rewritable compact disc according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a rewritable compact disc according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram of a push-pull signal of a rewritable compact disc according to one embodiment of the present invention.

FIG. 4 is an explanatory diagram of a reproduction signal of a rewritable compact disc according to one embodiment of the present invention.

FIG. 5 is a schematic perspective view for explaining a case where grooves are provided so as to connect pits to a ROM area in the rewritable compact disc according to one embodiment of the present invention.

FIG. 6 is a schematic diagram for explaining a case where grooves are provided so as to connect pits to a ROM area in the rewritable compact disk according to one embodiment of the present invention, wherein (a) is a plan view thereof; (b) is a cross-sectional view taken along the line AA of (a).

FIG. 7 is a schematic perspective view for explaining a case in which a groove is provided between pit rows in a ROM area in a rewritable compact disc according to one embodiment of the present invention.

FIG. 8 is a schematic diagram for explaining a case in which a groove is provided between pit rows in a ROM area in a rewritable compact disc according to one embodiment of the present invention;
(A) is the top view, (b) is BB arrow sectional drawing of (a).

FIG. 9 is a diagram for explaining a pit row having wobbles of a rewritable compact disc according to one embodiment of the present invention, wherein (a) shows an I ₁ -I ₂ signal obtained from the pit row; It is an explanatory view, and (b) is a schematic plan view showing the configuration of the pit row.

FIG. 10 is a schematic perspective view for explaining grooves and pits provided on a substrate of a rewritable compact disc according to one embodiment of the present invention.

11A and 11B are schematic views for explaining grooves and pits provided on a substrate of a rewritable compact disc according to an embodiment of the present invention, wherein FIG. 11A is a plan view thereof, and FIG. 4) is a sectional view taken along the line CC in FIG.

FIG. 12 is a schematic diagram for explaining an optical groove shape measuring method for optically measuring the groove shape of a rewritable compact disc using diffracted light according to an embodiment of the present invention.

FIG. 13 is a configuration diagram schematically showing an example of a laser optical system used in an embodiment of the present invention.

FIG. 14 is a schematic perspective view for explaining an exposure method in a method for manufacturing a rewritable compact disc according to one embodiment of the present invention.

FIG. 15 is a schematic perspective view for explaining another exposure method in the method for manufacturing a rewritable compact disc according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser generator 2 Laser beam 3 Substrate 9 Laser generator 10, 12, 13, 19, 22 Laser beam 11, 18, 23, 24 Beam splitter 14, 17 Light modulator 15, 20, 21 Reflector 16 Optical polarizer Reference Signs List 25 Objective lens 26 Glass substrate coated with photoresist film 50 Substrate (disk substrate) 51, 53 Protective film 52 Phase change recording layer 54 Reflective film 55 Protective coat 60 Pit (or pit row) 61 Groove (guide groove) 62 , 64 land 63 recording mark 70, 71 groove 80 substrate (glass substrate) 81 resist film 90 wobble 101 management area 102 user area 103 lead-in area 104 ROM area 105 RAM area 106 lead-out area

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) G11B 7/24 561 G11B 7/24 561Q 563 563C 7/007 7/007 7/26 501 7/26 501 (72) Invention Person Maeda Kubo 1000 Kamoshita-cho, Aoba-ku, Yokohama-shi, Kanagawa F-term in Yokohama Research Laboratory, Mitsubishi Chemical Corporation 5D029 JB09 JC02 WA02 WA18 WB11 WB17 WC01 WD22 5D090 AA01 BB11 CC14 DD01 GG40 5D121 BB01 BB21

Claims (16)

[Claims] 1. A rewritable compact disc having at least a phase-change recording layer on a substrate, wherein a recordable, erasable, and reproducible RAM area and a reproducible ROM area are on the same disk surface. The phase change type recording layer is provided in both the RAM area and the ROM area, and the RAM area is provided with a groove having a wobble, and the crystal state of the phase change type recording layer is provided. Are set to an unrecorded state / erased state, the amorphous part is set to a recorded state, and a recording light is irradiated to form an amorphous mark in the groove.
M-modulated information can be recorded. EFM-modulated information is recorded in a pre-pit row in the ROM area, and has a wavelength of 770 to 790 nm and an objective lens numerical aperture of 0.49.
When measured using an optical pickup of 0.51 to 0.51, the ratio of the push-pull signal value before and after recording the EFM modulated signal in the RAM area | I ₁ -I ₂ | / | I ₁ -I ₂ ｜ _a
Is 1.05 or more and 2.0 or less,
Rewritable compact disc. 2. The ratio | I ₁ between the push-pull signal value after recording in the RAM area and the push-pull signal value in the ROM area.
_2. The rewritable compact disc according to claim 1, wherein -I ₂ | _a / | I ₁ -I ₂ | _ROM is 0.78 or more and 1.3 or less. 3. A rewritable compact disk having at least a phase-change recording layer on a substrate, wherein a recordable, erasable, and reproducible RAM area and a reproducible ROM area are on the same disk surface. The phase change type recording layer is provided in both the RAM area and the ROM area, and the RAM area is provided with a groove having a wobble, and the crystal state of the phase change type recording layer is provided. Are set to an unrecorded state / erased state, the amorphous part is set to a recorded state, and a recording light is irradiated to form an amorphous mark in the groove.
M-modulated information can be recorded. EFM-modulated information is recorded in a pre-pit row in the ROM area, and has a wavelength of 770 to 790 nm and an objective lens numerical aperture of 0.49.
The value of the push-pull signal after recording in the RAM area and the value of the ROM
Ratio to the push-pull signal value of the region | I ₁ −I ₂ | _a / | I ₁
-A rewritable compact disc characterized by having an I ₂ | _ROM of 0.78 or more and 1.3 or less. 4. The 11T of the EFM modulation signal in the ROM area
The rewritable compact disc according to any one of claims 1 to 3, wherein a signal modulation degree is 0.55 or more and 0.95 or less. 5. A ratio (m ₃ / m ₁₁ ) between the 3T signal modulation degree and the 11T signal modulation degree of the EFM modulation signal in the ROM area.
The rewritable compact disc according to any one of claims 1 to 4, wherein the _ROM is 0.45 or more. 6. The 11T of the EFM modulation signal in the RAM area
The rewritable compact disc according to any one of claims 1 to 5, wherein a signal modulation degree is 0.60 or more and 0.90 or less. 7. A ratio (m ₃ / m ₁₁ ) between a 3T signal modulation degree and an 11T signal modulation degree of the EFM modulation signal in the RAM area.
The rewritable compact disc according to any one of claims 1 to 6, wherein the _RAM is 0.45 or more. 8. The maximum reflection of the ROM area and the RAM area
Rate ratio R_topROM/ R _topRAMIs 0.7 or more and 1.45 or less
The method according to any one of claims 1 to 7, wherein
The rewritable compact disc described. 9. The rewritable compact disc according to claim 1, wherein a value of a radial contrast of the ROM area is 0.30 or more and 0.60 or less. 10. The rewritable compact disc according to claim 1, wherein the prepit row in the ROM area has wobbles. 11. normalized wobble signal values obtained from the wobble of the ROM area NWS _ROM, characterized in that 0.035 or 0.060 or less, rewritable compact disk according to claim 10. 12. The pre-pit row in the ROM area has a pit depth of 60 to 100 nm and a pit width of 0.4.
5 to 0.70 μm.
12. The rewritable compact disc according to any one of 11 above. 13. The wobble groove in the RAM area has a groove depth of 30 to 50 nm and a groove width of 0.40 to 0.60.
The rewritable compact disc according to claim 1, wherein the size of the rewritable compact disc is μm. 14. A rewritable compact disc having at least a phase-change recording layer on a substrate, wherein a recordable, erasable, and reproducible RAM area and a reproducible ROM area are on the same disk surface. The phase change type recording layer is provided in both the RAM area and the ROM area, and the RAM area is provided with a groove, and a portion of the phase change type recording layer in a crystalline state is provided. The EFM-modulated information can be recorded by forming an amorphous portion in the groove by irradiating a recording light with an unrecorded state / erased state, an amorphous portion in a recorded state, and recording light. EFM-modulated information is recorded in a ROM area in a pre-pit row, and the pre-pit row in the ROM area has a pit depth of 60 to 1
00 nm and a pit width of 0.45 to 0.70 μm
A rewritable compact disc, characterized in that the groove in the RAM area has a groove depth of 30 to 50 nm and a groove width of 0.40 to 0.60 μm. 15. A master master on which a pre-pit row and a groove are formed is formed by irradiating a laser beam in accordance with a pre-pit row and a groove to be formed on a resist film formed on a substrate, exposing and developing the same, A method of manufacturing a rewritable compact disc having a phase-change recording layer after forming a stamper based on a master master and further forming a substrate provided with the prepit rows and grooves based on the stamper, 15. The method of manufacturing a rewritable compact disc according to claim 1, wherein when irradiating the resist film with a laser beam in accordance with the groove, the adjacent laser beams are directed in the traveling direction of the laser beam. A rewritable compact disc that is exposed by irradiating multiple laser beams so that they partially overlap each other in the vertical direction. Manufacturing method. 16. A master master on which a pre-pit row and a groove are formed by irradiating a laser beam in accordance with a pre-pit row and a groove to be formed on a resist film formed on a substrate, and exposing the laser beam to develop, A method of manufacturing a rewritable compact disc having a phase-change recording layer after forming a stamper based on a master master and further forming a substrate provided with the prepit rows and grooves based on the stamper, When manufacturing the rewritable compact disc according to any one of claims 1 to 14, when irradiating the resist film with a laser beam according to the groove, the rewritable compact disk is perpendicular to a direction in which the laser beam travels. 2.5 × 10 ⁶ times / m or more 2
A method for manufacturing a rewritable compact disc, comprising irradiating and exposing while oscillating at 5 × 10 ⁶ times / m or less.