JP3489415B2 - Optical information recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high density optical disc using a rewritable phase change medium. More specifically, the present invention relates to a phase change medium that is less likely to be deteriorated by rewriting data many times.

[0002]

2. Description of the Related Art In recent years, a recording medium capable of recording and reproducing a large amount of data at a high density and at a high speed has been demanded as the amount of information increases, and an optical disk is expected to meet such a purpose. . Optical disks are classified into a write-once type in which recording can be performed only once and a rewritable type in which recording and erasing can be performed repeatedly. Examples of the rewritable optical disk include a magneto-optical recording medium that utilizes the magneto-optical effect and a phase change medium that utilizes the reflectance change associated with the reversible change of the crystalline state. The phase change medium does not require an external magnetic field and can be recorded / erased simply by modulating the laser light power.
It has an advantage that the recording / reproducing apparatus can be downsized. Further, there is an advantage that the medium which can be recorded and erased at a wavelength of about 800 nm, which is the mainstream at present, can be densified by a short wavelength light source without changing the material of the recording layer and the like.

As such a phase-change recording layer material, a chalcogen-based alloy thin film is often used. For example, GeSbTe system, InSbTe system, GeSnTe
Examples thereof include AgInSbTe alloys. In the rewritable phase-change recording medium that is currently in practical use, no recording or
The erased state is changed to a crystalline state, and an amorphous bit is formed.
The amorphous bit heats the recording layer to a temperature higher than the melting point,
It is formed by quenching. In order to prevent evaporation and deformation of the recording layer due to such heat treatment, the upper and lower sides of the recording layer are usually sandwiched between heat-resistant and chemically stable dielectric protective films. In the recording process, this protective layer promotes thermal diffusion from the recording layer and realizes a supercooled state, which also contributes to the formation of amorphous bits.

Further, by forming a four-layer structure in which a metal reflection layer is provided on top of the above sandwich structure, it is usual to further promote thermal diffusion and form amorphous bits stably. The erasing (crystallization) is performed by heating the recording layer to a temperature higher than the crystallization temperature of the recording layer and lower than the melting point. In this case, the dielectric protective layer acts as a heat storage layer that keeps the recording layer at a high temperature sufficient for solid phase crystallization. In a so-called one-beam overwritable phase change medium, the erasing and re-recording processes described above can be performed only by intensity modulation of one focused light beam (Jpn.J.Appl.Phys., 26 (19).
87), suppl.26-4, pp.61-66). In the one-beam overwritable phase change medium, the layer structure of the recording medium and the circuit structure of the drive are simplified. Therefore, it is attracting attention as an inexpensive and high-density large-capacity recording system.

[0005]

In the recording process of the above phase change medium, the recording layer is melted and rapidly cooled to the melting point or lower within a few tens of nanoseconds, which is a radical thermal cycle. Therefore, even if the recording layer is sandwiched by the dielectric protective layers, microdeformation or segregation is accumulated by repeated overwriting several thousands to tens of thousands of times, and finally, an increase in optically recognizable noise or This leads to the occurrence of micron-order local defects (J.Appl.Phys., 78 (1995), pp6980-698.
8). Although significant improvements have been made by devising the material for the recording layer and protective layer, or the layer structure, there is essentially an upper limit on the number of rewritable times, which is higher than that of ordinary magnetic recording media and magneto-optical recording media. Less than an order of magnitude.

Further, the deterioration due to repeated overwriting also depends on the groove shape. For example, recently, a rewritable compact disc (CD-Rewritable, CD-RW) has been proposed ("CD-ROM professional" magazine (US),
September 1996, pp. 29-44, or Proceedings of Phase Change Optical Recording Symposium, 1995, 41-45.
page). In a CD, information is reproduced by scanning a concavo-convex pit array formed on the substrate at a pitch of 1.6 ± 0.1 μm from the back surface of the substrate with a focused light beam having a wavelength of 780 ± 30 nm. At this time, the reflectance at the non-pit portion is 7
It is specified by the standard that it is 0% or more.

Although it is difficult for the CD-RW to be compatible with a CD including a high reflectance of 70% or more, the reflectance in the unrecorded portion is set to 15% or more and 25% or less, and the reflectance in the recording portion is increased. If the ratio is less than 10%, the compatibility of the recording signal and the groove signal with the CD can be ensured. At least, if an amplifying system for covering the low reflectance is added to the reproducing system, the current CD drive can be used. Compatibility can be ensured in the technical category. In the CD-RW, the groove is used as a recording track to perform in-groove recording, but it is considered that a meandering containing address information is used for this groove (Japanese Patent Laid-Open No. 5-210849).

The schematic diagram is shown in FIGS. 1 (a) and 1 (b).
A meandering groove 1 is provided on the surface of a substrate 3 with a space 2 between the grooves. However, the amplitude of the meander is exaggerated. The meandering is called wobble (Wobble), and the carrier frequency is 2
It is frequency (FM) modulated at 2.05 kHz, and its amplitude (Wobble Amplitude) is compared with the pitch of the grooves 1 (distance between the virtual center lines of the grooves 1 sandwiching the grooves 2; usually about 1.6 μm). It is very small and about 30 nm.

This meandering is frequency-modulated by absolute time information or address information, and it is ATIP (Absolute
Time In Pre-groove) or ADIP (Address In
Pre-groove), which is already used for recordable compact discs (CD-Recordable, CD-R) and mini discs. ("CD Family" by Heitaro Nakajima, Takao Ihashi, Hiroshi Ogawa, Ohmsha (1996) Chapter 4,
And Proceedings of the IEEE. Volume 82 (199
(4 years) 1490 pages)

According to the study by the present inventors, a new deterioration phenomenon has been found in which the wobble signal leaks to the recording signal by repeating the overwriting. As a result, the number of repeatable times is further reduced by one digit or more, to about 1000 times. For CD-RW, w
The obverse is used to add address information that is essential for detecting an unrecorded area in which information is to be recorded. This phenomenon that the number of times of repeated overwriting is limited, will be
It is believed to be a more serious problem when using bble.

On the other hand, in an ordinary recording medium, the most frequently repeated recording is when the file management area for recording the table of contents information of the user data is rewritten, and the content itself of the user data is 1000. It is unlikely that it will be rewritten many times. For example, considering the CD format as an example, TOC (Table of Content
s) area and PMA (pr
It is possible that only the file management area such as the ogram memory area) is frequently rewritten. These file management areas are generally very limited areas provided on the innermost circumference or outermost circumference of the recordable area of the optical disc, and are less than a few% of the total recordable area.

That is, actually, in the CD format, the deterioration due to the groove meandering becomes a problem only in the TOC region. However, this area is a very important area where the table of contents of user data is recorded, and if an error occurs, the data in the entire data area cannot be read,
I cannot use the disc. That is, the number of times the file management area can be overwritten limits the life of the disk. As a countermeasure, it is conceivable to reserve a spare track as an alternate area of the file management area and use this when the error increases due to overwriting, but the number of times is also limited and the file management procedure is Complicated and difficult to design the drive and device driver. In other words, it is the actual situation that the number of rewritable overwrites of the entire disk is limited due to the area of less than several percent that is frequently rewritten.

[0013]

The first gist of the present invention is as follows.
A medium for optical information recording having a rewritable phase-change recording layer on a substrate, wherein a groove for guiding a focused light beam is concentrically or spirally formed on the substrate, and the groove is formed along the groove. The file management area has a constant groove shape, and the data area causes the groove shape to meander by a signal representing address information and synchronization information, and the groove meandering signal carrier level pair. The noise ratio is 25 dB or more, and the meandering amplitude aw of the groove, the beam diameter R0 of the focused beam light in the groove transverse direction, and the groove width GW have the following relationship:

[0014]

[Equation 3]   0.25 ≦ GW / R0 ≦ 0.45 or 0.65 ≦ GW / R0 (1)   0.03 ≦ aw / GW ≦ 0.08 (2)

The present invention resides in an optical information recording medium characterized by satisfying at the same time. A second aspect of the present invention is an optical information recording medium having a rewritable phase-change recording layer provided on a substrate, the substrate having grooves for guiding a focused light beam in a concentric or circular shape. Data tracks are provided in a spiral shape, and data tracks are arranged along the groove. The data tracks are composed of user data areas and additional data areas alternately arranged in the circumferential direction. At least in the user data area, a groove meandering signal is provided. The carrier level-to-noise ratio is 25 dB or more, and the meandering amplitude aw of the groove, the beam diameter R0 of the focused beam light in the groove crossing direction, and the groove width GW have the following relationship:

[0016]

[Equation 4]   0.25 ≦ GW / R0 ≦ 0.45 or 0.65 ≦ GW / R0 (1)   0.03 ≦ aw / GW ≦ 0.08 (2)

The present invention resides in an optical information recording medium characterized by simultaneously satisfying the following conditions. The groove meander means that the groove is meandered in the groove transverse direction at a constant cycle, and frequency modulation is performed based on this cycle to record various information such as address information, synchronization information, and special information as a signal. , Usually called wobble. These are obtained by transferring the groove formed by vibrating the exposure beam for forming the groove in the groove transverse direction or modulating the intensity at the time of forming the master, for example, by injection molding onto the substrate. vice versa,
The constant groove shape means that the groove is formed in a substantially constant shape without including such wobble modulation.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a groove meandering (w) is used as a rotation synchronizing signal or a signal obtained by frequency-modulating address information.
It uses a method of recording in the form of an (able). (For example, refer to JP-A-2-87344). These can be formed by vibrating an exposure beam for groove formation in the groove crossing direction at the time of forming the stamper, and can be reproduced in a large amount by transferring the exposure beam onto a resin substrate by injection molding, for example.
(JP-A-63-103454, JP-A-2-87344,
JP-A-2-198040, JP-A-3-88124, JP-A-3-237657, JP-B1-223859, JP-B3
-3168, etc.).

ATIP described by wobble
The signal or the ADIP signal is used for controlling the rotation speed of the unrecorded area and for addressing the data area. ("Compact Disc Reader" by Heitaro Nakajima and Hiroshi Ogawa, Ohmsha (1988), or the above-mentioned published patents, etc.). The wobble may be formed with a single frequency without being frequency-modulated, and may be used simply for establishing rotation synchronization of the disc. Before explaining this, the ATIP signal or ADIP signal described by wobble, and the TOC
Will be explained in a little more detail. The ATIP signal described by wobble is used for controlling the rotation speed of the unrecorded area and for addressing the data area. The scheme will be explained in a little more detail as follows ("Illustrated compact disc reader", written by Heitaro Nakajima and Hiroshi Ogawa, Ohmsha (Revised 3rd edition, 1996), "CD family" mentioned above, or the above-mentioned published patents. Etc.).

FIG. 2 is a schematic view showing the recording areas in the radial direction of the CD and the recordable CD for comparison. As shown in the figure, the areas on the disc of the CD and the recordable CD are PCA or PMA (a2) and lead-in area (a3, Lead) from the innermost clamping area (a1) toward the outer peripheral side. -in area), program area (a
4, program area: corresponding to the data area in the present invention) and the lead-out area (a5), and the physical position on the track corresponds to the absolute time information of ATIP. The user's file is the program area a5
Recording is performed from the position corresponding to the origin on the time, which is the innermost circumference of, toward the outer circumference. As the file is recorded, the TOC whose address is described in absolute time on ATIP is written in the lead-in area a3 immediately before that. The start position (time) of the lead-in area is the start position (time) of the TOC.

Once the address information is written in the TOC by the EFM modulated signal, the time information of ATIP and the EF
This is in agreement with the absolute time of the subcode-Q channel which is filled in with M modulation (and thus recorded with digital information). In both ATIP and EFM modulated data, absolute time is described every 1/75 seconds. A group of this data is called one frame of ATIP, one block of EFM data or one subcode frame. The absolute time and the rotation synchronization signal for each frame are irrelevant to the scrambling process for error correction, so that the absolute time is always arranged to increase from the inner circumference to the outer circumference. The program area has an unrecorded area until it is completely filled with user files, and access to the unrecorded area is A
It is performed with reference to the absolute time of the TIP signal. Access to the recorded area is performed by referring to the absolute time of the subcode-Q channel.

Similarly, the rotation speed control in the unrecorded area is AT
This is performed by reading the sync pattern at the beginning of one frame of the IP signal. In the already recorded area, the ROM (Read Only) is detected by detecting the synchronization pattern for each block.
Like a Memory disk, it can detect absolute time (or address) and sync. Therefore, once the subcode-Q information is written in the EFM signal, the absolute time information of the subcode-Q channel may be used thereafter, and it is not necessary to refer to the ATIP signal thereafter. R
When reproduced by the OM drive, only the address information and user data recorded by the EFM signal are reproduced.

The inventors of the present invention have used a CD-type disc using a phase change medium.
RW (rewritable compact disc, CD-Rewritable)
In the development process of, due to the existence of the wobble,
We found that deterioration was promoted during repeated overwriting, and found that this could become a more serious problem when the density of tracks is increased in the future. It was also found that the acceleration of this deterioration can be suppressed under certain conditions. The structure of the optical information recording medium having the phase change recording layer of the present invention and the information recording method will be described. As the substrate, a transparent resin such as polycarbonate, acrylic, or polyolefin, or glass can be used.

The phase change recording layer is preferably covered with protective layers on the upper and lower sides thereof. Preferably, it has a structure of substrate 3 / lower protective layer 4 (dielectric layer) / recording layer 5 / upper protective layer 6 (dielectric layer) / reflective layer (7) as shown in FIG.
It is desirable that it is covered with a protective coat layer 8 made of an ultraviolet or thermosetting resin or the like. Reflective layer 7
Is provided to increase the signal amplitude by more positively utilizing the optical interference effect, and to function as a heat dissipation layer so that a supercooled state necessary for forming an amorphous mark can be easily obtained. This is because

Therefore, the reflective layer 7 has a high reflectance,
A metal having high thermal conductivity is desirable, and specifically, Au, Ag,
Examples thereof include Al. However, in order to increase the degree of freedom in optical design, a semiconductor such as Si or Ge may be used. From the economical and corrosion resistance viewpoints, an Al alloy in which 0.5 to 5 atomic% of Ta, Ti, Cr, Mo, Mg, Zr, V, Nb, etc. is added to Al is desirable. Among these, particularly, the addition of Ta gives a highly corrosion-resistant material (Japanese Patent Laid-Open No. 1-169751). A protective layer satisfying the above characteristics is usually provided on the surface of the substrate in a thickness of 10 nm to 500 nm. The material of the protective layer 4 or 6 includes a refractive index,
It is determined in consideration of thermal conductivity, chemical stability, mechanical strength, adhesiveness, and the like.

In general, oxides, sulfides, and nitrides of metals and semiconductors having high transparency and high melting point, Ca, Mg, Li
Fluoride such as can be used. These oxides,
Sulfides, nitrides, and fluorides do not necessarily have to have a stoichiometric composition, and it is also effective to control the composition or mix them for controlling the refractive index and the like. Considering the repetitive recording characteristics, the dielectric mixture is preferable. More specifically, a mixture of ZnS or a rare earth sulfide and a heat resistant compound such as an oxide, a nitride, or a carbide can be used. The film density of these protective layers is preferably 80% or more of the bulk state from the viewpoint of mechanical strength (Thin Solid Films, Vol. 278 (19).
1996), pp. 74-81).

The thickness of the dielectric layer varies depending on the method of using the medium, but when it is less than 10 nm, the effect of preventing deformation of the substrate and the recording film is insufficient, and it does not serve as a protective layer. Therefore, it is 10 nm or more. If it exceeds 500 nm, the internal stress of the dielectric itself and the difference in elastic properties from the substrate become remarkable, and cracks are likely to occur. More preferable conditions for the protective layer (dielectric layer) are
The lower protective layer 4 needs to suppress substrate deformation due to heat, and is preferably 70 nm or more. When the thickness is less than 70 nm, microscopic substrate deformation is accumulated during repetitive overwriting, and reproduction light is scattered, so that noise may be significantly increased. The upper limit of the thickness of the lower protective layer 4 is substantially about 200 nm due to the film formation time,
If it is thicker than 0 nm, the groove shape seen on the recording layer surface is changed, which is not preferable. That is, it is not preferable because the groove depth becomes shallower than the intended shape on the substrate surface, or the groove width becomes narrower than the intended shape on the substrate surface. More preferably, it is 150 nm or less.

On the other hand, the upper protective layer 6 needs to have a thickness of at least 10 nm or more in order to suppress the deformation of the recording layer. If it is thicker than 60 nm, microscopic plastic deformation is likely to be accumulated in the upper protective layer during repeated overwrite,
This is not preferable because it also scatters the reproduction light and increases noise. The recording layer of the medium of the present invention is a phase change type recording layer, and the thickness thereof is preferably in the range of 10 nm to 100 nm. If the thickness of the recording layer is less than 10 nm, it is difficult to obtain a sufficient contrast, and the crystallization speed tends to be slow, which makes it difficult to erase the recording in a short time. On the other hand, if the thickness exceeds 100 nm, it becomes difficult to obtain optical contrast and cracks are likely to occur, which is not preferable. Further, in order to obtain a contrast that is compatible with CD, the thickness is preferably 10 nm or more and 30 nm or less. If it is less than 10 nm, the reflectance becomes too low,
If it is thicker than m, the heat capacity becomes large and the recording sensitivity tends to deteriorate. A known phase change type optical recording layer can be used as the recording layer, and for example, GeSbTe, InSbTe, AgSbT can be used.
Compounds such as e and AgInSbTe are selected as overwritable materials.

Among them, {(Sb2Te3) 1-x (G
eTe) x} 1-ySby (0.2 <x <0.9, 0 ≦
y <0.1) alloy or Mw (SbzTe1-z) 1-
w (0 ≦ w <0.3, 0.5 <z <0.9, M is In,
Ga, Zn, Ge, Sn, Si, Cu, Au, Ag, P
d, Pt, Pb, Cr, Co, O, S, Se, V, N
The thin film containing at least one alloy selected from b and Ta) as a main component is stable in both crystalline and amorphous states, and
A fast phase transition between both states is possible. Further, it is the most practical material because it has the advantage that segregation hardly occurs when overwriting is repeated.

The recording layer is often obtained by sputtering an alloy target in an inert gas, especially Ar gas. The thicknesses of the recording layer and the protective layer have good absorption efficiency of the laser light and the amplitude of the recording signal in consideration of the interference effect due to the multilayer structure, in addition to the above-mentioned limitations in terms of mechanical strength and reliability. That is, it is selected so that the contrast between the recorded state and the unrecorded state is large. As described above, the recording layer, the protective layer and the reflective layer are formed by the sputtering method or the like. It is desirable to form a film by an in-line apparatus in which the target for the recording film, the target for the protective film, and if necessary, the target for the reflective layer material are installed in the same vacuum chamber in order to prevent oxidation and contamination between the layers. It is also excellent in terms of productivity.

Generally, in a phase change medium,
By repeated overwrite, microscopic deformation is accumulated on the protective layer and the substrate surface, the focused light beam is scattered to increase the noise of the reproduction light, or the optical film thickness of the recording layer and the protective layer is changed, There arises a problem that the mark length cannot be detected accurately. The degree of deterioration due to repeated overwriting depends on the cross-sectional shape of the groove. We have wobb
When recording was performed in a groove without le, the deeper and narrower the groove width, the slower the progress of deterioration due to repetitive overwriting, which means that the groove shape is defined. It is considered that this is due to the effect of confining the recording layer by the groove wall. That is, it is considered that as the groove is deeper and narrower, the melted region at the time of recording is limited by the groove width, and the width of the deformed region at the groove bottom portion due to the melting of the recording layer is suppressed.

On the other hand, the deformation of the groove shape due to overwriting also extends to the groove wall. Since it is considered that the groove wall has poor adhesion of the thin film and stress concentration easily occurs at the corners, it is likely that heat damage will be concentrated during repeated overwriting. Is believed to be promoted. In particular, in the case where the groove is formed on the resin substrate or the photo-curing resin, the softening point of the resin is much lower than the temperature (several hundreds of degrees Celsius) at the time of recording of the phase change medium, and therefore the groove shape is deformed by repeated overwrite More or less always occurs.

The inventors of the present invention have studied the bottom of the groove with an atomic force microscope.
When the deformation of the groove wall portion was measured, it was confirmed that unevenness of 2 to 3 nm was formed after repeated overwriting, and the groove wall portion was deformed. The range of the groove width limited by the overwrite durability is determined by the relative relationship between the groove width GW and the focused light beam diameter R0 in the groove transverse direction. As shown in FIG. 4, normally, the energy intensity distribution of the focused light beam for optical recording is a Gaussian distribution, but the degree of deterioration is determined by which part of the Gaussian distribution hits the groove wall. However, the beam diameter R0 in the groove crossing direction here
Is the diameter at which the intensity of the Gaussian beam is 1 / e2. (It is not the Airy disk diameter described later)

First, in a state where the groove wall is irradiated with light energy sufficiently lower than the intensity of the peak of the Gaussian beam, naturally, the deterioration of the groove wall can be ignored. The condition is that the groove wall is located outside the position where the light energy intensity is approximately 40% of the center, and this condition corresponds to 0.65 ≦ GW / R0 in the Gaussian distribution. To further consider this physical meaning, consider the temperature distribution of the recording layer during recording. According to the calculation obtained by solving the thermal diffusion equation of the temperature distribution, the center temperature of the beam irradiation portion is close to 1000 ° C. when the amorphous mark is formed. Since the thermal conductivity of the recording layer and the protective layer is smaller than that of Al or the like by two to three orders of magnitude, it is possible to apply the first-order approximation that the temperature distribution ignoring the thermal conductivity corresponds to the Gaussian distribution.

At this time, the temperature is about 400 ° C. or less in the vicinity of the diameter of 0.65 × R0 around the beam irradiation portion, and the melting point (500) of the above-mentioned recording layer material which is usually used as a phase change medium in the portion corresponding to the groove wall. ~ 700
℃). When the groove width becomes narrower than this, the deterioration due to the irradiation of the groove wall gradually becomes remarkable. On the other hand, according to the study by the present inventors, the improvement effect by the confinement effect of the recording layer by the groove wall appeared, and when GW / R0 ≦ 0.45, deterioration (increase in noise) due to repeated overwrite was suppressed rather.

To summarize the above, in order to improve the overwrite durability in the recording in the groove, in FIG.
GW / R0 ≦ 0.45 or 0.65 ≦ GW / R
It is necessary to satisfy the relationship of 0. However, if the groove width is too wide, tracking servo is less likely to be applied, and the recording track density is lowered, so that the G is almost G.
It is desirable that W / R0 <1.0.

The present inventors have further found that GW / R0 ≦ 0.
In the case of 45, if the groove width is too narrow, wobbl
We found a new deterioration phenomenon due to the presence of e, and
I found out that the lower limit of W / R0 was decided. wobbl
Although the mechanism of deterioration promotion due to the presence of e is not always clear, as shown in FIG.
It is considered that this is because a part of the above is likely to be irradiated on the side wall 10 of the groove 1. That is, the focused light beam 9 to which the tracking servo is applied does not follow the wobbling meandering of the wobble, but goes straight along the center line 11 of the groove. Groove wall 10
If there is a meander, the light beam 9 is likely to be irradiated on the groove wall 10 though it is small, as shown in FIG.

Although the wobble amplitude aw is exaggerated in FIG. 5, this tendency is considered to be correct. Usually wo
Since the amplitude of bble is on the order of 1-10 nm,
Due to the deformation of the groove wall of 2 to 3 nm as described above, wob
The ble signal quality is significantly degraded. In this case, wobb
not only the CN ratio (carrier to noise ratio) of the le signal itself decreases, but also the SN ratio (si of the signal recorded in the groove).
gnal to noise ratio).

When the signal waveform was observed, as shown in FIG. 6, the envelope oscillated due to the periodic meandering of the groove, but the oscillation of this envelope had a narrow groove width and wobb.
The larger the le amplitude is, the more remarkable it is. It was found that the periodic fluctuation of the envelope itself became irregular with the deterioration of the wobble, and eventually leaked into the recording signal itself as noise. Ultimately wobb
If le itself does not exist, such deterioration does not occur,
As mentioned above, unless the amorphous mark protrudes from the groove,
The groove width is narrow so that GW / R0 ≦ 0.45, or 0.65 ≦ G so that deterioration of the groove wall can be completely ignored.
The wider W / R0, the less deterioration due to repeated overwrite.

However, according to the present inventors, wobble
In the case of the presence of the groove, since the wobble signal deterioration due to the groove wall deterioration is more remarkable than the recording layer confinement effect due to the groove wall of the narrow groove, the groove wall is irradiated with too strong light intensity in FIG. Is not preferable. Therefore, the groove width has a lower limit of 0.25 ≦ GW / R0.
After all, from the viewpoint of repeated overwrite durability, it is necessary to limit the groove width to the following range.

[0041]

[Equation 5]   0.25 ≦ GW / R0 ≦ 0.45 or 0.65 ≦ GW / R0                                                               (1)

Of these, 0.25≤GW / R0≤0.45
The above condition is more advantageous from the viewpoint of higher density. In FIG. 4, when GW / R0 <0.25, the deterioration of the envelope following wobble becomes extremely remarkable, and 0.4
When 5 <GW / R0 <0.65, the effect of confining the recording layer by the groove wall is insufficient, and the deterioration is remarkable due to the synergistic effect of the two factors of partial deterioration of the groove wall.
When 0.65 ≦ GW / R0, the confinement effect due to the groove wall disappears, but deterioration of the groove wall can be substantially ignored, so that the repeated durability is improved again.

On the other hand, the deterioration due to the wobble is wo
It also depends on the bble amplitude aw. Ie, wobbl
The larger the ratio aw / GW between the amplitude aw and the groove width GW, that is, the more uneven wobbles entered in the groove, the more noticeable the noise leakage into the recording signal due to the deterioration of the wobble deformation. Therefore, aw /
Wo by overwriting that GW ≦ 0.08
It is necessary to prevent envelope deterioration due to bble. On the other hand, if the wobble amplitude aw is too small, the strength of the wobble signal itself becomes weak.

On the other hand, CN (carr of the wobble signal itself
There is a lower limit because a certain amount or more is required to obtain an ier to noise ratio of 25 dB or more, while on the other hand, there is an upper limit because deterioration due to overwriting becomes significant if the amplitude is too large and it projects too much into the groove. .

[0045]

[Equation 6] 0.03 ≦ aw / GW ≦ 0.08 (2)

The numerical values themselves were determined by experiments as in the examples. This relationship does not depend on the wavelength or NA of the light beam, but is merely the beam diameter R0 and the groove width G in the groove crossing direction.
It is considered to be determined by the relative relationship between W and the wobble amplitude aw. Groove meander in the present invention
It is extremely difficult to directly measure the amplitude of the with an electron microscope or a scanning probe microscope. Therefore, in the present invention, the wobble amplitude is defined by the following measurement. That is, in the given optical head, the relationship between the displacement amount aw from the average center of the groove in FIG. 5 and the wobble signal amplitude Iw is given as the off-track amount of the tracking servo system and the servo error signal.

[0047]

[Equation 7]       Iw = A · sin (2 · π · aw / p) (10)

From the above equation, the wobble amplitude of the groove (amount of displacement from the average center of the groove) aw is obtained. However, p is a predetermined track pitch, that is, the distance from the land center on one side of the groove to the land center on the other side. FIG. 6 is a diagram showing a servo error signal. A is half of the peak-to-peak servo error signal of the push-pull method measured in the state where the tracking servo is not applied (open loop),
It is expressed by the following formula.

[0049]

[Equation 8]     (I1-I2) pp = 2 · A (11)

Iw is the amplitude of the signal generated by the wobble of the groove in the servo error signal (I1-I2), that is, the wobble signal amplitude. Specifically, it can be measured as the amplitude of the servo error signal obtained in the state where the groove is tracked. From the above, the values of P, A, and Iw are determined by measuring the servo error signal, and these can be substituted into the equation (3) to obtain aw. According to this method, aw is determined in principle regardless of the characteristics of the optical head, the beam shape, and the groove shape. The measuring method itself is a technique well known to those skilled in the art. In the above description, CD-RW is cited as an example, but as described above, the definition of terms is clear and easy to use for description.

On the other hand, not only the current CD but also a high density CD-like recording medium can generate a rotation synchronizing signal and give an address signal by groove wobbling, and the present invention is also effective in this case. Needless to say. In the present invention, the groove depth also has a preferable range from the viewpoint of repeated overwrite durability. In a phase change medium, generally, recording in the groove is between the grooves (so-called on land).
Greater overwrite durability than recording. Although the cause is not always clear, it is considered that the groove wall protects the end portion of the recording layer effectively. If the groove depth is less than 25 nm, this protective effect may not be sufficient.

On the other hand, if the groove depth exceeds 200 nm, it becomes difficult to attach the sputtered film to the groove wall, the film thickness seen from the groove wall becomes thin, and a poor film with low density is likely to be formed, which is not preferable. . In addition, it is not desirable because it is difficult to transfer the groove shape by injection molding. In the present invention, in particular, in order to further improve the durability in the file management area where overwrite is frequently performed, wobble is eliminated in the file management area, the groove shape is made constant, and the overwrite is performed in the remaining data area. The wobble and groove shape are designed considering durability.

As can be seen from the above description, if the cue of the TOC area (lead-in area), that is, even the start position can be detected, the TOC itself will not always be AT.
Noted that no IP signal or wobble is needed. In addition, when the TOC information is reproduced, the starting position of the TOC information needs to be known.
This is because the TIP signal is not referenced. Further, there is a wobble in the innermost circumference of the lead-in area, and the rotation speed is controlled by the synchronization signal there, and once the rotation speed reaches a steady state, there is no feedback from the ATIP signal synchronization pattern in the TOC area. However, the disturbance that causes a problem in synchronizing the clock signal and the rotation speed does not occur. This is because the correct synchronization is detected again at the position when accessing the program area with reference to the TOC.

FIG. 7 is an explanatory diagram showing an example of a CD-RW to which the present invention is applied. A spare area 12, a file management area (lead-in area) 13, and a data area 14 are provided from the inner peripheral side on a groove formed in a spiral shape. Areas other than the file management area 13 are ATI by wobble of the groove.
P is recorded. The spare area 12 is used for attracting the focused light of the drive and adjusting the recording power. When EFM-modulated data is recorded in the unrecorded data area, first, addressing is performed by ATIP and recording is performed, but the ATIP signal is not necessarily required in the recorded data area. This is because the portion called the sub-code Q channel in the EFM modulated signal contains absolute time information, so that addressing can be performed by detecting the EFM modulated signal in the recorded data area. Regarding the synchronization, similarly, in the unrecorded area, the synchronization information is detected from the wobble to control the rotation of the disk, but in the recorded area, the rotation control can be performed by detecting the subcode Q channel of the EFM modulation signal.

Similarly, in the file management area 13, if EFM modulated data is recorded, addressing and rotation control can be performed without ATIP. That is, some kind of recording is performed in advance in the file management area with the EFM modulated signal, or only by the first access to the file management area, the recording is performed by using some means for the recording, and the recorded signal is used from the next time onward. You can do it like this. For example, the cue information of the file management area is set to the groove wo
A special information area recorded as bble may be provided at a predetermined position on the medium. In this case, the drive may first access the special information area and search for the file management area. The special information area is preferably located at a position where the drive first accesses, and is preferably provided in the spare area 12 in FIG. 8, for example. If the file management area is located in the outermost area and the drive is accessed from the outermost area, it is desirable to provide the special information area in the outermost area.

As disclosed in Japanese Patent Laid-Open No. 3-3168, various information for drive control such as optimum recording power of the disc can be superposed and recorded on the ATIP signal of the file management area. In this case, if there is deterioration due to repetitive overwriting, these various types of information cannot be reproduced, which is a problem. Such various information for drive control can also be recorded in the special information area. The recorded information may be read once by the drive and then recorded in the file management area as an EFM modulated signal in a form included in the file management information.

Alternatively, after the medium is manufactured, an EFM modulation signal containing absolute time information, that is, address information may be recorded in the file management area as an initialization operation. For example, the start address of the data area may be entered as the start address of the unrecorded portion. Of course, various kinds of drive control information may be recorded together. In this case, it is preferable that the drive used by the user does not need to have a special function. On the other hand, although some changes are required on the drive side, special information and prepits for rotation synchronization may be provided in advance in the file management area. In this case,
As shown in, the file management information of the user is synchronized with the pre-pit row 15 arranged at regular intervals,
It is recorded in the area between them. By setting the interval between the discrete prepit rows to be, for example, an integral multiple of the EFM frame, it is possible to record without any contradiction with the conventional EFM signal.

Further, the wobb of the groove is formed just before the file management area or up to the very beginning of the file management area.
It is also possible to provide le and perform addressing. It is desirable that the connection / synchronization between the absolute time information of the EFM modulated signal recorded in the file management area and the absolute time information of ATIP in the data area be as smooth as possible and not jump in absolute time. As the synchronizing method, the method described in JP-A-3-88124 can be used. Since the file management information is the table of contents of the user data, the less the amount of user data recorded, the less the file management information. However, in the present invention, in order to provide continuity in the absolute time information between the file management area and the data area, the EFM modulation signal is also written in the form of dummy data even in the file management information unrecorded portion of the file management area. It is desirable to keep a record. The recording order of the dummy data and the file management information is arbitrary. For example, if the file management information is recorded from the beginning of the file management area, it is preferable to record dummy data containing synchronization information and address information from the end to the end of the file management area.

On the other hand, from the viewpoint of the continuity of the address information, the end of the file management information may coincide with the end of the file management area. In this case, it is preferable to record dummy data from the beginning of the file management area to the beginning of the file management information. When the above-described initialization operation is performed, only the dummy data need be recorded in the entire area. The present invention also provides an optical information recording method which uses the above medium and shifts the recording start position every time part or all of the file management information including dummy information is rewritten. It is known that when repetitive overwriting is performed, it is effective to shift the recording start position little by little in order to delay the signal deterioration due to mass transfer of the phase change medium (Japanese Patent Laid-Open Nos. 2-94113 and 3-93).
150725 publications). By applying this recording method to the file management area of the medium of the present invention, signal deterioration can be further reduced. If the amount of shift is too large, the allowable range of the absolute time information will be exceeded, so there is some limitation. However, a sufficient improvement effect can be obtained at about 10 to 100 μm, for example.

Although the CD-RW has been described above as an example,
As described above, the present invention is not limited to this. The data signal may be a modulation signal including address information and synchronization information, and is not limited to the EFM modulation signal. Providing the groove-shaped signal modification is one method of increasing the recording density of the recording medium, and can be applied to recording media having other formats. Even in this case, the present invention is of course effective. For example, ISO9660 (High Shera File Format) is a logical format standard including the CD standard. In the current CD standard, only the physical file structure is described in the file management area, and the physical position of data in block units is described as absolute time information. The hierarchical structure of files, so-called directory structure, cannot be described.

In ISO9660, the physical structure is described in the file management area, and the directory structure is described as the path table in the specific area of the data area. In this case, it is obvious that the path table of this specific area is also included in the file management area referred to in the present invention. Further, Japanese Patent Laid-Open No. 5-210849 discloses that file management information is temporarily or transiently recorded in a specific area other than the final file management area. In this case, the repeated overwrite durability of the specific area poses a problem, but the file management area of the present invention includes such a specific area.

According to the present invention, it is not necessary to secure and manage the replacement area such as re-recording the file management information in the replacement area that has not deteriorated, so that the file management procedure becomes very easy and the drive and The device driver can be easily designed. Of course, it is up to the person skilled in the art to consider the design in order to further improve the reliability by using the specifications of the replacement area together. The second gist of the present invention relates to a method of so-called packet write, in which data is randomly additionally written in block units. Record information only once on the disc,
Alternatively, add additional data to the unrecorded area (increment
That is already realized in the CD-R. In this case, the data capacity recorded at one time varies. Further, since the user data is always recorded continuously from the inner circumference to the outer circumference, the unrecorded area is always located at the outer circumference side position continuous with the recorded area, and the recorded area is located outside the unrecorded area. Will never exist. Therefore, it is easy to selectively use the sync and absolute time with the EFM signal in the recorded area and the sync and absolute time with the ATIP signal in the unrecorded area.

On the other hand, in recent years, even in the CD format, a hard disk (HD), a floppy disk (FD) or a magneto-optical disk (MO) is divided into fixed capacity (for example, a unit of 2n bytes) called a sector. It is required to record user data. In particular, in order to take advantage of the rewritable characteristic of the CD-RW, it is necessary to manage data in units of fixed length sectors. This is because if the data to be overwritten is not physically within a certain length range, there is a risk of overwriting even over the data that should not be erased. Delimiters for each sector, sector addresses, and even synchronization signals are described in advance in a drive in HD or FD, or in advance in an MO or the like by a pit row on a substrate.

FIG. 9 shows an example of sectors in MO.
Pit column and user data area 1 that compose the header 16
7 and 7 are alternately arranged in the circumferential direction, and one set of the header 16 and the data area 17 constitutes a sector 18.
The length of the header 16 is exaggerated in the drawing.
In the CD format, a method for realizing data management in the above-mentioned sector method such as MO is not necessarily determined, but the US industry group OSTA (Optical Storage Tech) is used.
nology Association) is a method that has been publicly proposed and discussed.

One is CD-DASD (Compact Disc D
This is a proposed standard called irect Access Storage Disc, in which each sector is in units of 4096 bytes that are relatively compatible with the DOS format (February 1996).
Proposed by Kodak in an open presentation at STA). The other is a method being studied in CD-R, which is called the packet write method ((1) DOS / V magazine, June 1996 issue, page 214,
(2) Chapter 4 of the "CD Family" above, and
(3) Nikkei Electronics September 9, 1996 (No.67
0), 135-146). A similar packet writing method is also discussed in the next-generation DVD standard (Nikkei Byte, June 1996 issue, pp.198-203).

These are necessary for constructing a logical format for performing non-sequential recording, which does not depend on the operation system, regardless of whether the data format on the disc is CD format, DOS format, or the like. It is also a request. As described above, the sync signal corresponding to the information described in the sector area,
Additional information such as address information is written on the disc in advance at regular intervals by pits, ATIP signals, ADIP signals, or the like. In a normal recordable CD medium, an ATIP signal is engraved as a wobble without being interrupted from end to end of a track. Current CD-
To facilitate compatibility with the R device, the pits and wobble signal patterns peculiar to the sector area are not used,
It is desirable to use the address information in the ATIP, ADIP or EFM signals.

FIG. 10 is a schematic plan view of a disc according to an embodiment of the present invention, which is easily compatible with the existing CD-R. Reference numeral 19 indicates a guide groove, and 20 indicates a land portion,
In the circumferential direction of each data track, the additional data area 21
The user data areas 22 are arranged alternately. When the present invention is applied to the phase change type rewritable medium adopting the above-mentioned fixed length pseudo sector structure, in FIG.
The additional data area 21 has a wob modulated by a predetermined signal.
A guide groove portion 23 having a ble is formed, and at least in the user data area 22, at least the following two equations are simultaneously satisfied:
A groove having a bble.

[0068]

[Equation 9]   0.25 ≦ GW / R0 ≦ 0.45 or 0.65 ≦ GW / R0 (1)   0.03 ≦ aw / GW ≦ 0.08 (2)

Linear velocity (CLV, Constant Linear Velocit
Since it is used in y) mode, user data of a fixed byte length always corresponds to a fixed absolute time length. Therefore, even if the additional information is included, one unit of user data corresponds to a fixed absolute time length. Therefore, as shown in FIG. 10, the additional data 25a + the user data 22+ is set at every constant absolute time T described in the ATIP signal of the guide groove on the disc.
A pseudo sector (or packet) 26 consisting of one set of additional data 25b is arranged. However, the additional data area 25 may be either the front or the back. Here, the user data area 22 is in units of 2n bytes, for example.

In the present invention, using the concept and terminology of HD and MO, the above-mentioned set of data is called a packet, the physical structure on the disc on which the packet is recorded is a pseudo sector, and the additional data area is a pseudo header. I will call it. In fact, when overwriting packets, it is necessary to pay attention to the data gap that can be created at the time of writing. In the drive, when actually recording by modulating the laser light,
Due to the drive system of the laser and the rise time of the laser, there are subtle errors in the start and end positions of writing. It is preferable to provide a gap (buffer) area before and after the additional data so that the information of the adjacent pseudo sector is not destroyed by this shift. For example, when packet writing is performed in units of 32 Kbytes, an error of about several tens of bytes may occur (Nikkei Bytes, June 1996 issue, pp.198-203).

Apart from the above gap, CLV at linear velocity V
In the operating drive, the physical virtual sector length along the track is constant at VT, and the additional data area 21
Will be arranged at regular intervals VT along the track. Since each pseudo sector length is constant, the absolute time of the head position of each sector can be assigned by calculation, or can be described in the lead-in area. Of course, when the entire surface of the disk is operated by CLV like a CD, the same access method is possible even in the ZCLV mode in which the disk is divided into zones in the radial direction. Further, in a disk operating in CAV or ZCAV, address information may be described by an ADIP signal that does not depend on absolute time. In this case, ISO
Like the standard MO medium, the address information at the beginning of each sector is read from the ADIP signal instead of the prepits.

The present invention relates to a so-called packet write method using the above-mentioned pseudo sector, but is not directly related to the detailed methods of the above various proposals, but overwrites for repeatedly recording fixed length data (packet). The purpose is to improve the repetitive overwrite durability in possible phase change type media. In the additional data area (pseudo header section), a wobble having a larger amplitude than that of the user data area can be formed to ensure the reading of the address information.
It is also possible to eliminate the above and describe by pre-pits in the groove or between the grooves. Further, in some cases, the groove itself may be eliminated and additional data such as address information may be described by the pre-pits embedded in the mirror surface. By doing so, the pseudo header section eliminates interference between the wobble signal and the recording signal, and more accurate access becomes possible. Alternatively, as the initialization operation, the address information may be recorded in the additional data area by the same recording method as the data.

As for the groove shape having wobbling interruptions as in the present invention, recently, Japanese Unexamined Patent Publication No. 8-32947 has been proposed.
3, disclosed in JP-A-9-120585, but the present invention is essentially different from this prior application for the following reasons. That is, first, the problem to be solved by the present application is a phenomenon in which the repeated overwrite durability of the phase change medium deteriorates due to wobble, but in JP-A-9-120585, the phase change medium is applied to an example. However, the present invention is not limited to this and, therefore, does not mention the repetitive overwrite deterioration peculiar to the phase change medium. Regarding the formal similarity of wobbling of the prior application, each of the prior applications corresponds to the distinction between the user data area and the additional data area.
There is no point of view to make bel intermittent, so wob
It is also assumed that the ble area is overwritten. At that time, in consideration of overwrite durability, w
There is no idea to limit the shape of the groove and groove.

The wobble amplitude can be switched between the pseudo header section 21 and the user data section 22 by a simple modification of the existing mastering signal source. As shown in the block diagram of the master exposure apparatus of FIG. 11, the above groove formation is performed by a modulation signal generation circuit CM1 that generates a modulation signal for forming a wobble and a laser that irradiates the exposure laser light of the glass master 23. This is possible by providing the gate G1 between the vibration drive circuit CW1. in this case,
Absolute time information is continuously generated from the modulation signal M1 as before, and the sector header switching unit CM2
A gate signal M2 that causes the gate G1 to open at the pseudo header position is generated. As a result, the wobble modulation signal M1 is intermittently supplied to the laser beam drive circuit CW1.

The groove width can be controlled by making a stamper.
Basically, it can be easily achieved by increasing or decreasing the power of the laser beam for exposure when exposing the photoresist on the glass master. That is, at the switching point between the additional data area and the user data area, the wobble vibration is large or small 2
The intensity of the laser beam may be switched between two values, strong and weak, while switching to one of the stages. Then, the amplitude of the exposure beam at the time of forming the groove is reduced in the user data area 22 by the wobble amplitude amount.
Change the groove width by changing the exposure light quantity (1)
It suffices to form a groove shape that satisfies the expressions (2) and (2). However, even when the wobble amount of the laser light beam for exposure is switched, the absolute time of the wobble modulation signal is advanced so that the absolute time in each pseudo sector becomes an exact position function when rotated by the CLV method. To

When the packet write method is applied to the recording medium of the present invention to record information, the AT in the pseudo header area is recorded.
From the IP or ADIP signal, or the prepit,
Read address information, user data area wob
A predetermined rotation synchronization is established from ble. Next, after the address is calculated, recording is performed by the EFM signal on the entire pseudo sector starting at the desired absolute time. At the first recording in the packet, the synchronization and the absolute time may be recorded in the pseudo header portion having wobble by the EFM signal. After that, the desired sector can be accessed by referring to the data of this EFM signal without depending on the ATIP signal.

R capable of reproducing packet-written data
In order to access a desired pseudo sector and read data with the OM drive, the access can be performed by reproducing the EFM signal regardless of the ATIP signal. However, from the point of the present invention, the E of the pseudo header part with wobble is
It is not desirable to rewrite the FM data every packet write. After the second recording, if the additional data is already recorded in the pseudo sector portion by the EFM signal, only the user data is overwritten. On the other hand, it is also possible to use it by always rewriting only user data and not recording it in the pseudo header part. In this case, access is always ATIP
Signal or ADIP signal. This method requires adding an ATIP signal or ADIP signal reproducing / decoding circuit to the ROM drive, which is a burden on the drive, but is effective as one option. The current CD family has cleared the requirement of accumulating minor additions and improvements on the drive side in consideration of compatibility with the past, so this option is not a big problem.

If the present invention is introduced in advance when a standard different from the current CD is adopted for higher density, it is easy to deal with the ROM drive. Where A
The absolute time connection / synchronization recorded by using the TIP signal and the EFM modulation signal should be as smooth as possible and not jump in absolute time. Such a synchronization establishing method is described in JP-A-3-88124.
On the contrary, when the repetitive overwriting is performed, intentionally and randomly shifting the recording start position within the allowable range delays the signal deterioration due to the mass transfer during the repetitive overwriting known in the phase change medium. (See Japanese Patent Application Laid-Open Nos. 2-94113 and 3-150725).

This allowable value is not quantitatively clear at present, but in the case of the CD format, the CD-R
As inferred from the standard, it is about 1 to 2 EFM frames (588 channel bit length) (100-200 μm),
Even if the recording start position is shifted within this range, a sufficient improvement effect can be obtained. In the CD format, or a format that complies with the ISO 9660 and ISO 13346 standards, which is a superordinate concept of the CD format, file management information is written at the beginning of the lead-in area and program area at the innermost circumference of the disc. This is based on the UDF (Universa
It is considered a subset of the logical format called Disk Format). In this format, file management information such as the top address, length, attribute, and directory structure of the file is logically described in a grouped address, and every time the file is rewritten, part or all of the file management information is rewritten.

When reproducing the information, first, the file management information is accessed to obtain information regarding the address of a predetermined file, and then the address is actually accessed to read the user data. The file management area is also called a disk management area. A series of file management information is
Even on an actual disc, it is usual that the discs are collectively arranged at a specific position on the innermost or outermost periphery of the disc. For example, in the CD format, it is arranged as a TOC in the lead-in area a3 in FIG. In ISO9660, the directory structure is described at the beginning of the program area. In the present invention, a specific area in which the file management information is written is called a file management area.

As a further improvement of the present invention, the first invention and the second invention may be combined to eliminate all the periodic deformations of the groove in the file management area. In this way, the reliability of the file management area where the deterioration of the recording characteristics due to repetitive overwriting is most predominant because it is rewritten frequently can be improved, and the reliability of the entire disc is further enhanced. The lead-in area a3 in FIG.
In the case of temporarily rewriting the file management information in the PMA area a2 without rewriting
It is desirable to apply the present invention also to this area as a file management area.

For the file management area without the modulation of the groove shape, the recording power, the used linear velocity, etc. are previously stored in the file management area without the modulation of the groove shape as an operation of the disk initialization at the time of factory shipment of the disk. EF the disc information
It is good to fill in with M modulation. For example, the top address of an unrecorded user area is to be entered in the TOC,
In this case, the manufacturer of the disc may prepare a special drive and record the start position of the disc information / pseudo-sector together with the absolute time information at the beginning of the file management area, which does not burden the user. Such a technique is used for various operating systems even in the current FD and MO discs.

When the packet write method is applied to the overwritable phase change medium of the present invention, for example, in the case of the CD-RW using the recording pulse strategy shown in FIG.
When repeatedly overwriting at a double speed of the CD linear velocity (1.2 m / s to 1.4 m / s), the deterioration starts after 1000 times of repeated overwriting, but the recording characteristics almost deteriorate even after 10,000 times or more. Does not happen. In some cases, characteristic deterioration hardly occurred up to about 100,000 times. Therefore, it is possible to secure and manage a replacement area by re-recording a pseudo sector whose characteristics have deteriorated due to repeated overwrites accidentally concentrating on that area, as was done in the past, in another replacement area that has not deteriorated. The need is almost gone. For this reason, the file management procedure is facilitated, and the design of the drive and device driver is facilitated. With CD-RW media,
A method of recording / rewriting in sector units like a magneto-optical disk has not been established yet, but if such a method is established, it is expected that the number of times of rewriting will reach an enormous number (for example, 100,000 to 1,000,000 times or more).
In that case, the present invention can be expected to suppress deterioration due to repeated overwrite easily and at low cost.

(Experimental example) In the present invention, the conditions of the formulas (1) and (2), which are numerical limitation conditions, in particular, the condition of 0.65 ≤ GW / R0 in the formula (1) is irrelevant to the existence of wobble. The present invention relates to a general phase change medium for recording a groove, and its significance is described in detail in the text. In the following, 0.25 ≦ GW / R0 ≦ 0.45 in (1) and 0.03 ≦ aw / GW ≦ 0.08 in equation (2), which are determined by the deterioration phenomenon derived from the presence of wobbles, in particular 2 The requirements will be described with reference to an experimental example using a substrate having wobbled grooves.

Experimental Example 1 The recording medium used in the following experiments has the layer structure shown in FIG. Lower protective layer ZnS: SiO ₂
(200 nm), recording layer Ag ₅ In ₆ Sb ₆₀ Te ₂₉ alloy (20 nm), upper protective layer ZnS: SiO ₂ (20n)
m), 4 of reflective layer Al _98.5 Ta _1.5 alloy (200 nm)
The layer structure was created by the sputtering method. A protective coat made of an ultraviolet curable resin was further applied thereon.

Overwriting was repeated in the groove. wobble is an unmodulated signal of 22.05 kHz,
It is transferred by injection molding onto a polycarbonate substrate having a diameter of 120 mm and a thickness of 1.2 mm. Groove pitch is 1.
At 6 μm, the groove width is about 0.5 μm and the depth is about 40 nm. Recording was performed by forming an amorphous mark in the groove. Recording was performed using an optical disk drive DDU1000 manufactured by Pulstec Co., Ltd. equipped with an optical head having a wavelength of 780 nm, NA = 0.55, and a beam diameter R0 in the groove transverse direction of 1.35 μm.

Recording was performed using a pulse division method as shown in FIG. 13, with recording power Pw = 12 mW, erasing power Pe = 6 mW, and bias power Pb = 0.8 mW. The deterioration of the 3T signal was measured when the EFM random signal was repeatedly overwritten at twice the CD speed (2.8 m / s). The signal quality was evaluated by jitter. It is necessary according to the CD standard that the jitter is less than 17.5 nsec at double speed. 3T mark jitter at the time of first recording is 9-
11 nsec. Met.

By repeatedly overwriting with the pulse strategy of FIG. 13, the 3T mark jitter is 17.5 nse.
The number of times reaching c (the number of repeatable times) was measured. CD
-Durability of 1000 times or more is required according to RW standard,
Also in this example, 1000 times or more were passed. wobbl
The e-amplitude was also measured by the method described in Orange Book. The groove width was determined by the optical diffraction method (U groove approximation). Table 1 shows various GW / R0 and aw / GW
The repeatable number of times is summarized with respect to the value.

In Table 1, the portion surrounded by the thick line is the portion satisfying the requirements of the expressions (1) and (2) (Experimental Example 1), and the other portions are Comparative Example 1. In the groove having no wobble amplitude, there is almost no deterioration in jitter even after overwriting 5000 times, but the deterioration becomes remarkable as the wobble amplitude increases, and when GW / R0 = 0.50, the deterioration becomes remarkable after about 1500 times. Recognize. The progress of deterioration due to the presence of wobbles is slow when the groove width to the beam width is 0.25 or more and 0.45 or less, and is less than 0.25 and 0.45.
If it is larger, it may be faster and may be cut less than 1000 times.
On the other hand, when aw / GW is 0.08 or more, deterioration due to overwrite progresses rapidly. When the aw / GW is less than 0.03, the wobble has a low carrier-to-noise ratio. C / N
Is less than 25 dB, it may be difficult to accurately reproduce the groove meandering signal, the rotation of the disk may not be synchronized, or the address information may not be read.

[0090]

[Table 1]

(Experimental Example 2) Track pitch 1.0 μm,
Groove width 0.33 μm, groove depth 45 nm, period 22.05 k
A meandering groove with a frequency of 25 nm and an amplitude of 25 nm (aw / GW = 0.0
76), and a lower protective layer ZnS: Si
O ₂ (150 nm), recording layer Ge ₂₃ Sb ₂₅ Te ₅₂ 2 alloy (20 nm), upper protective layer ZnS: SiO ₂ (20n)
m), 4 of reflective layer Al _98.5 Ta _1.5 alloy (200 nm)
The layer structure was created by the sputtering method. A protective coat made of an ultraviolet curable resin was further applied thereon.

Overwriting was repeated in the groove at a linear velocity of 2.8 m / s in the same manner as in Experimental Example 1. As a recording optical system, wavelength 680 nm, NA = 0.6, R0 = 1.05
Recording power Pw = 11 m with a beam of μm (Experimental example 2)
A pulse strategy (pulse division method) with W, erase power Pe = 4 mW, and Pb = 0.8 mW was used. On the other hand, the recording optical system has a wavelength of 780 nm and NA = 0.5.
5, R0 = 1.35 μm beam (Comparative Example 2), recording power Pw = 13 mW, erasing power Pe = 6 mW, Pb =
A pulse strategy of 0.8 mW was used. In any of the optical systems, the CN ratio of wobble was 25 dB or more. In the system of Experimental Example 2, GW / R0 = 0.31, and in the system of Comparative Example 2, GW / R0 = 0.24. In Experimental Example 2, it could be repeated 5000 times or more. On the other hand, in Comparative Example 2, it was about 700 times. Also, after several hundred times w
A significant decrease in the ob ibleC / N was seen.

[0093]

According to the present invention, in a recording medium having a wobble in which the deterioration of a phase change medium during repeated overwriting is particularly problematic, the deterioration is suppressed and the reliability of the disk is improved.
The durability can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory view of a wobble, (a) is a plan view,
(B) is an AA 'sectional view.

FIG. 2 is a schematic cross-sectional view showing the radial area distribution of a CD and a recordable CD.

FIG. 3 is an explanatory diagram showing an example of a layer structure of an optical information recording medium of the present invention.

FIG. 4 is a diagram showing an energy intensity distribution of a focused light beam.

FIG. 5 is an explanatory diagram showing a state where a recording light beam is applied to a wobbled recording groove.

FIG. 6 is a diagram showing a servo error signal.

FIG. 7 is an explanatory diagram showing an example of an optical information recording medium to which the present invention is applied.

FIG. 8 is an explanatory diagram showing an example of an optical information recording medium to which the present invention is applied.

FIG. 9 is a plan view showing a sector structure of a conventional magneto-optical disk (MO).

FIG. 10 is a plan view showing a data track according to the embodiment of the present invention.

FIG. 11 is a block diagram showing the configuration of a master exposure apparatus used to manufacture the optical information recording medium of the present invention.

FIG. 12 is an explanatory diagram of a recording pulse strategy used in this experimental example.

[Explanation of symbols]

1 Groove 2 Between Grooves 3 Substrate 4 Lower Protective Layer 5 Recording Layer 6 Upper Protective Layer 7 Reflective Layer 8 Protective Coating Layer 9 Focused Light Beam 10 Groove Wall 11 Groove Centerline 12 Spare Area 13 File Management Area (Lead-in Area) 14 data area 15 synchronization pit row 16 header 17 user data area 18 sector 19 guide groove 20 inter-groove (land) portion 21 additional data area 22 user data area 23 guide groove 24 having wobbles wobble width aw and groove width GW are limited Guide groove 25a Pre-additional data 25b Post-additional data 26 Pseudo sector (packet) 27 Glass master

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Claims (15)

(57) [Claims] 1. A medium for optical information recording having a rewritable phase change recording layer on a substrate, wherein the substrate is provided with grooves for guiding a focused light beam in a concentric or spiral shape. , A data area and a file management area are formed along the groove, the groove shape is fixed in the file management area, and the groove shape is meandered in the data area by a signal indicating address information and synchronization information. The signal carrier level-to-noise ratio is 25 dB or more, and the meandering amplitude aw of the groove, the beam diameter R0 of the focused beam light in the groove transverse direction, and the groove width GW have the following relationship: ## EQU1 ## GW / R0 ≦ 0.45 or 0.65 ≦ GW / R0 (1) 0.03 ≦ aw / GW ≦ 0.08 (2) At the same time, an optical information recording medium is characterized. 2. The optical information recording medium according to claim 1, wherein the groove width in the file management area is narrower than the groove width in the data area. 3. The optical information recording medium according to claim 1, further comprising a special information area in which cue information in the file management area is recorded by groove-shaped signal deformation. 4. The optical information recording medium according to claim 1, wherein the address information is recorded in the file management area by the same recording method as the data as the initialization operation. 5. A rewritable phase-change compact disc, wherein the meandering of the guide groove is ATIP.
2. The optical information recording medium according to claim 1, wherein the file management area is a lead-in area including TOC information, which constitutes a signal or an ADIP signal and starts from the inner side in the radial direction of the data section. 6. An information recording method using the optical information recording medium according to claim 1, wherein the recording start position is shifted every time part or all of the file management information is rewritten. 7. An optical information recording medium having a rewritable phase change recording layer provided on a substrate, wherein the substrate is provided with grooves for guiding a focused light beam in a concentric or spiral shape. , A data track is arranged along the groove, and the data track is composed of a user data area and an additional data area alternately arranged in the circumferential direction. At least in the user data area, carrier level vs. noise of a groove meandering signal. The ratio is 25 dB or more, and the meandering amplitude aw of the groove, the beam diameter R0 of the focused beam light in the groove transverse direction and the groove width GW are as follows: 0.25 ≦ GW / R0 ≦ 0. 45 or 0.65 ≦ GW / R0 (1) 0.03 ≦ aw / GW ≦ 0.08 (2) at the same time, which is an optical information recording medium. 8. The optical information recording medium according to claim 7, wherein a buffer area for error correction is provided in the additional data area. 9. The optical information recording medium according to claim 7, wherein a groove meandered by the address information or the synchronizing signal is present in the additional data area. 10. The optical information recording medium according to claim 7, wherein address information or a synchronization signal is described in the additional data area by prepits. 11. A rewritable phase-change compact disc, wherein the meandering of the guide groove is ATI.
The optical information recording medium according to claim 7, which constitutes a P signal or an ADIP signal. 12. The wavelength of laser light used for recording and reproduction is 770 nm to 800 nm, and the numerical aperture of the focusing lens is 0.
40 to 0.60 and the groove width is 0.4 μm to 0.
The optical information recording medium according to claim 11, wherein the optical information recording medium has a groove depth of 7 μm and a groove depth of 30 nm to 70 nm. 13. The optical device according to claim 7, wherein a file management area for managing the user data area is provided on the inner side in the radial direction of the data track, and the groove shape is constant in the file management area. Information recording medium. 14. The optical information recording medium according to claim 14, wherein absolute time information is recorded in the file management area by the same modulation signal as in the additional data area. 15. A rewritable phase-change compact disc, wherein the meandering of the guide groove constitutes an ATIP signal or an ADIP signal, and the file management area is a lead-in area containing at least TOC information. The optical information recording medium according to claim 13.