JP2001056958A - Optical information recording medium and optical recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a medium and a method that allows high speed overwriting, that has small mark edge jitters, that enables high density mark length modulation recording, and that excels greatly in the secular stability of a formed mark. SOLUTION: The optical information recording medium is such that it is at least provided with a phase change type recording layer on a substrate, that the crystal part of this recording layer is made an unrecorded/erased state while the amorphous part a recorded state, and that information is recorded by a plurality of recording mark lengths having the shortest mark length of 0.5 μm or less. In this case, the optical information recording medium and the optical recording method suitable for it are such that erasure is performed through recrystallization which essentially proceeds by crystal growth from the boundary between the amorphous part or a fused part and the peripheral crystalline part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rewritable DV.
The present invention relates to an optical recording medium and an optical recording method for high-density recording having a phase-change recording layer, such as D, in particular, linear velocity dependence and recording power dependence during one-beam overwriting, and aging stability of recording marks. An optical recording medium and an optical recording method improved in the above.

[0002]

2. Description of the Related Art In general, a compact disk (CD) or D
In the VD, recording of a binary signal and detection of a tracking signal are performed by utilizing a change in reflectance caused by interference of reflected light from the bottom and the mirror surface of the concave pit. In recent years, as a medium compatible with a CD, a phase-change rewritable compact disc (CD-RW, CD-Rewritab)
le) is becoming widely used. As for DVDs, various phase-change rewritable DVDs have been proposed.

These phase-change type rewritable CDs and Ds
The VD detects a recorded information signal by utilizing a change in a reflectance and a change in a phase difference caused by a difference in a refractive index between an amorphous state and a crystalline state. An ordinary phase change medium has a structure in which a lower protective layer, a phase change recording layer, an upper protective layer, and a reflective layer are provided on a substrate, and a reflectance difference and a phase difference are obtained by using multiple interference of these layers. It can be controlled to make it compatible with CDs and DVDs. In a CD-RW, compatibility between a CD and a recording signal and a groove signal can be ensured within a range where the reflectance is reduced to 15 to 25%, and reproduction is performed by a CD drive to which an amplification system for covering a low reflectance is added. Is possible.

Since the phase-change recording medium can perform the erasing and re-recording processes only by the intensity modulation of one focused light beam, the recording and reproducing on a phase-change recording medium such as a CD-RW and a rewritable DVD can be performed. Includes overwrite recording in which recording and erasing are performed simultaneously. For recording information using a phase change, a crystal, an amorphous state, or a mixed state thereof can be used, and a plurality of crystal phases can be used. In general, a recording medium is used for recording by setting an unrecorded / erased state to a crystalline state and forming an amorphous mark. As a material of the recording layer, a chalcogen element, that is, a chalcogenide-based alloy containing S, Se, and Te is often used.

[0005] For example, GeSbTe system mainly composed of GeTe-Sb ₂ Te ₃ pseudo-binary alloy, InTe-Sb ₂
InSbTe based on Te ₃ pseudo binary alloy, S
AgInSbT the b _{0. 7} Te _0.3 whose main component is a eutectic system
e-based alloys, GeSnTe-based alloys and the like. Of these, Ge
Te-Sb ₂ Te ₃ pseudo binary alloy system obtained by adding excess Sb in, in particular, Ge ₁ Sb ₂ Te _4, or Ge ₂ Sb
An intermetallic compound neighborhood composition such as ₂ Te ₅ are mainly commercialized.

[0006] These compositions are characterized by crystallization without phase separation, which is peculiar to intermetallic compounds, and have a high crystal growth rate, so that initialization is easy and the recrystallization rate during erasure is high. For this reason, as a recording layer exhibiting practical overwrite characteristics, a pseudo binary alloy system or a composition near an intermetallic compound has been attracting attention (see Jpn. J. Appl. Phys., Vol. 69 (1992)).
1), p2849, or SPIE, Vol. 2514 (1995), pp294-301
etc).

On the other hand, in these compositions, metastable tetragonal crystal grains grow. These crystal grains have clear crystal boundaries and irregular sizes, and have a problem in that optical anisotropy is remarkable depending on the orientation thereof, so that optical white noise is easily generated. Since such crystal grains having different particle diameters and optical characteristics tend to grow around the amorphous mark, the jitter of the mark is likely to increase, or the optical characteristics are different from those of the surrounding crystals. It was easy to be detected as remaining. For this reason, there is a problem that good reproduction characteristics cannot be obtained in recording at a high linear velocity or high-density mark length modulation recording. Specifically, in the rewritable DVD standard, the shortest mark length is 0.6 μm, but it has been found that jitter is sharply increased as the shortest mark length is further reduced.

As a measure for improving jitter, there is a so-called absorption rate correction. In the conventional four-layer structure, the light energy absorbed by the recording layer is generally smaller than the light energy Ac absorbed in the crystalline state with high reflectance (Ac) in the crystalline state with high reflectance. <A
a). Therefore, at the time of overwriting, there is a problem that the shape or the like of a new recording mark changes depending on whether the original state is a crystalline state or an amorphous state, and jitter increases. This makes the absorption efficiency of light energy in the crystalline state and the amorphous state substantially the same, stabilizes the mark shape regardless of the original state, and thereby reduces jitter. Furthermore, since the crystal needs extra heat for the latent heat at the time of melting, it is preferable that the crystal state absorbs more light energy (Ac> Aa).

In order to achieve this relationship, there is a method in which at least one light absorbing layer is added to form a structure of five or more layers, and a part of the light absorption in an amorphous state is removed by the absorbing layer. For example, an absorbing layer such as Au or Si is inserted between the lower protective layer and the substrate or on the upper protective layer (Jpn.J.Appl.Phys., V
ol.37 (1998), pp3339-3342, Jpn.L.Appl.Phys., Vol.37
(1998), pp 2516-2520).

However, such a layer configuration has a problem in heat resistance and adhesion of the absorbing layer, and when overwritten repeatedly, deterioration such as microscopic deformation and peeling is remarkable. In addition, the stability over time deteriorates because peeling or the like is likely to occur. That is, to achieve a high density while maintaining a conventional four-layer structure, it has been difficult in the GeTe-Sb ₂ Te ₃ pseudo binary alloy recording layer. Moreover, GeTe-Sb
_{In the} 2Te ₃ pseudo-binary alloy recording layer, since the birefringence has a wavelength dependency such that the shorter the wavelength, the smaller the real part becomes and the larger the imaginary part becomes. It is difficult to achieve the condition of Ac> Aa.

Therefore, in recent years, AgIn has been used as a recording layer material.
SbTe quaternary alloys are being used. AgInSb
The Te quaternary alloy is characterized in that a high erasure ratio as high as 40 dB can be obtained. The conventional four-layer structure enables high linear velocity and high-density mark length modulation recording without correction of absorptivity. . However, being able to perform high-speed recording usually means that the crystallization speed is high and erasing is easy. Therefore, amorphous marks are also easily crystallized, and the recorded marks often have poor temporal stability.

[0012]

In recent years, the amount of information has increased, and in order to shorten the recording time and speed up the information transfer, recently, a medium capable of recording and reproducing at a higher speed has been demanded.
For example, the standard speed (1x speed) of a CD is 1.2 to 1.4 m /
s, but a CD-RW capable of recording at 4 × speed has been commercialized, and a CD capable of recording at 8 × speed and 10 × speed
-RW is required. On the other hand, rewritable DVDs include DVD-RAM, DVD + RW, DVD-RW
Various types have been proposed or commercialized. However, the capacity is 4.7, which is equivalent to that of a read-only DVD.
GB rewritable DVDs have not yet been put to practical use.
In other words, there is a need for a medium that can record short marks at high speed and has good mark stability.

However, conventionally, high-speed recording and mark stability have been considered to be contradictory properties, and it has been considered difficult to satisfy both at the same time. The present inventors have repeatedly studied the principles of crystallization and amorphization, and have found an epoch-making medium that satisfies all of these characteristics at the same time. That is, the present invention provides an optical recording medium on which short marks can be satisfactorily recorded at high speed and which has good mark stability, and an optical recording method suitable therefor.

[0014]

The first gist of the present invention is as follows.
At least a phase change type recording layer is provided on the substrate, and a crystal part of the recording layer is in an unrecorded / erased state, an amorphous part is in a recorded state, and information is recorded by a plurality of recording mark lengths having a minimum mark length of 0.5 μm or less. An optical information recording medium for recording information, wherein erasing is performed by recrystallization substantially proceeding by crystal growth from a boundary between an amorphous portion or a molten portion and a peripheral crystal portion. An optical information recording medium characterized in that:

A second gist of the present invention is that Ge,
It has a phase-change type recording layer composed of a thin film containing Sb and Te as its main components. An optical information recording medium for recording information with a plurality of recording mark lengths, wherein the medium continuously emits recording light having a recording power Pw sufficient to melt a recording layer at a constant linear velocity. An optical information recording medium characterized in that it is substantially crystallized and an amorphous mark is formed when the recording layer is irradiated with recording light having a recording power Pw sufficient to melt the recording layer at a constant linear velocity and then cut off. .

According to a third aspect of the present invention, a first protective layer, a phase-change recording layer, a second protective layer, and a reflective layer are provided on a substrate in order from the incident direction of recording / reproducing light. The crystal part of the recording layer is in an unrecorded / erased state and the amorphous part is in a recorded state,
An optical information recording medium for recording information with a plurality of recording mark lengths having a minimum mark length of 0.5 μm or less, wherein a phase change type recording layer has a film thickness of 5 nm or more and 25 nm or less and a GeSbTe ternary phase diagram. In (Sb _0.7 Te
_0.3 ) and a straight line A connecting Ge, (Ge _0.03 Sb _0.68 Te
_0.29 ) and (Sb _0.95 Ge _0.05 ), a straight line B, (Sb
A straight line C connecting ( _0.9 Ge _0.1 ) and (Te _0.9 Ge _0.1 ),
And a thin film mainly composed of a GeSbTe alloy having a composition of a region (but not including the boundary) surrounded by four straight lines D connecting (Sb _0.8 Te _0.2 ) and Ge. The layer exists in an optical information recording medium characterized by having a thickness of 5 nm or more and 30 nm or less. Another aspect of the present invention resides in an optical recording method suitable for use in combination with the above medium.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have proposed that in a phase change medium in which the crystalline state of a recording layer is an unrecorded / erased state and the amorphous state is a recorded state, erasing is performed with an amorphous portion or a fused portion. It has been found that a medium which is substantially recrystallized by crystal growth from a boundary with a peripheral crystal part can perform high-speed, high-density and stable recording. That is, high-speed overwriting can be performed, high-density mark length modulation recording with small mark edge jitter can be performed, and the formed marks have very good temporal stability.

Generally, the erasing of the amorphous mark is performed by heating the recording layer to a temperature higher than the crystallization temperature and lower than the vicinity of the melting point to bring the recording layer into an amorphous solid state or a molten state, and then recrystallizing when cooling. Occur. According to the study of the present inventors, erasing of an amorphous mark, that is, recrystallization is performed by (1) generation of a crystal nucleus in an amorphous region, (2) an amorphous portion or a fused portion, and The process proceeds by two processes of crystal growth starting from the boundary with the part, but the former crystal nucleation hardly occurs, and the above-mentioned crystal growth process is substantially performed using only the latter process. It was found that such an effect was obtained.

Normally, crystallization proceeds at a temperature higher than the crystallization temperature and lower than the melting point, but crystal nucleation proceeds at a relatively low temperature and crystal growth proceeds at a high temperature within that temperature range. This is not to say that erasure cannot be performed without the generation of crystal nuclei. Erasing is possible if crystal growth proceeds at a high speed using a boundary point with a peripheral crystal region surrounding an amorphous portion or a molten portion as a nucleus. In particular, a finer mark or a shorter mark is more likely to be instantaneously crystallized to the center of the mark only by crystal growth from such a peripheral crystal part, and thus can be completely erased in an extremely short time. Therefore, only in a high-density recording medium using a minute mark whose shortest mark length is 0.5 μm or less,
The effect is remarkable, erasing can be performed in the order of 100 nanoseconds or less, and overwriting can be performed at high speed. In general, the shorter the mark length, the shorter the length of the mark, the higher the recording density. However, from the viewpoint of the stability of the mark, the shortest mark length is preferably 10 nm or more.

The narrower the width of the mark is, the easier it is to crystallize to the center of the mark only by crystal growth from the peripheral crystal part, which is preferable. Therefore, it is preferable that the track pitch of the track for recording information is, for example, 0.8 μm or less so that the mark does not spread horizontally. Normally, the mark width is about half the track pitch. In general, the narrower the track pitch is, the higher the recording density can be. However, from the viewpoint of mark stability, the track pitch is 0.1 μm.
m or more is preferable. The track may be a groove only, or may be both a groove and a land.

The medium of the present invention is also excellent in the stability over time of the amorphous mark. That is, crystal growth from the peripheral crystal part
Among the crystallization temperature or higher and the melting point or lower, even the amorphous mark formed once is hardly crystallized because it progresses only in a relatively high temperature region close to the melting point and hardly progresses at a low temperature,
Excellent stability over time. The crystallization temperature is usually 100 ° C to 20 ° C.
Although it is in the range of 0 ° C., the thermal stability can be maintained up to this temperature.

In particular, in a normal use range below 100 ° C., the recorded amorphous mark is extremely stable, and the amplitude of the recorded signal hardly deteriorates. Conversely, it can be concluded from the stability over time that almost no crystal nucleation occurs. Further, the medium of the present invention has an advantage that a smooth mark edge with extremely small fluctuation can be formed in mark length recording. In general, when recording an amorphous mark, the recording layer is once melted and re-solidified to be amorphous.
Conventionally, recrystallization due to crystal nucleus growth is likely to occur at the edge of the mark, and coarse grains mixed with amorphous are generated,
This caused mark edge fluctuation.

In the medium of the present invention, the fact that the crystal growth from the boundary between the amorphous portion or the molten portion and the crystal portion is dominant at the time of erasing and that the speed is high is based on the same principle at the time of recording. Also, when the molten region is re-solidified and becomes amorphous, only the crystal growth from the peripheral crystal portion occurs, and crystallization due to crystal nucleus growth hardly occurs, and the mark edge does not easily fluctuate. In other words, the crystal growth from the peripheral crystal part progresses only in a relatively high temperature range close to the melting point and hardly progresses at a low temperature even in the range from the crystallization temperature to the vicinity of the melting point. The boundary shape of the amorphous mark is determined only by the cooling rate at which the temperature decreases and passes the melting point.

[0024] Then, almost no coarse grains mixed with amorphous due to crystal nucleus growth occurring at the time of re-solidification, which is a problem in the past, are formed at all around the amorphous mark. This has been found to be extremely effective in suppressing noise due to mark edge fluctuation. Furthermore, since the mark edge shape is stable without changing over time,
Not only the initial jitter is small, but also the jitter is hardly deteriorated with time.

The crystallization principle of the present invention will be described in more detail. In the present medium, the boundary between the amorphous mark and the peripheral crystal portion becomes a nucleus for crystal growth, and almost no crystal nucleus is generated inside the amorphous mark. Therefore,
Crystals grow only from the mark boundaries. On the other hand, conventional G
eTe-Sb ₂ Te ₃ based recording layer, the crystal nuclei are randomly generated within the amorphous mark, crystallization advances it grows. The difference between the two crystallization processes can be confirmed with a transmission electron microscope. When both recording layers after the formation of the amorphous mark are irradiated with erasing light of a relatively low power in a DC manner, GeTe-Sb ₂
In the Te ₃ -based recording layer, it is observed that crystallization proceeds from the central portion of the amorphous mark where the temperature increases, whereas in the recording layer of the present invention, the crystal grows from the peripheral portion of the amorphous mark. Is observed. In particular, crystal growth from the front end and the rear end of the amorphous mark is remarkable.

The composition of the recording layer to be erased according to the above principle is such that the composition near the eutectic point of Sb _0.7 Te _0.3
And up to about 20 atomic% in alloys to which other elements are added. _{That, M y (Sb x Te 1} -x) 1-y
(0.6 ≦ x ≦ 0.9, 0 <y ≦ 0.2, M is Ga, Z
n, Ge, Sn, Si, Cu, Au, Al, Pd, P
t, Pb, Cr, Co, O, S, Se, Ta, Nb, V
(At least one of them). In an alloy containing excess Sb in Sb _0.7 Te _0.3 , the crystal growth from the crystal around the amorphous mark is GeTe-S
Since it is significantly larger than the b ₂ Te ₃ pseudo binary alloy system,
It has the feature that overwriting at high linear velocity is possible.
Excess Sb does not promote random crystal nucleation and crystal nucleus growth in the amorphous mark, but greatly increases the crystal growth rate from the peripheral crystal part. However, in the case of the SbTe binary alloy, since crystal nuclei are generated to a considerable extent, the stability of the amorphous mark with time is extremely poor, and it is necessary to add an appropriate element.

According to the study of the present inventors, the addition of Ge is extremely effective in suppressing the generation of crystal nuclei. Now, whether the recrystallization of the amorphous mark is substantially controlled only by the recrystallization from the peripheral crystal part can be indirectly known from the evaluation of the temporal stability. As a specific evaluation method, when performing an accelerated environmental test under high temperature and high humidity,
There is a method of measuring the modulation degree of the reproduction signal.

That is, when a signal is recorded with a plurality of mark lengths equal to or less than the shortest mark length of 0.5 μm or less, the modulation degree of the signal reproduced immediately after recording is M _0, and after recording, the modulation degree is 80 ° C.
The degree of modulation of reproduced signal after 1000 hours elapsed When M ₁ under the conditions of RH%,

[0029]

[Equation 11] M ₁ / M ₀ ≧ 0.9

## EQU1 ## The mark length modulation method is not limited.
EFM modulation, EFM plus modulation, (1, 7) RLL-N
RZI (run length limited-non return to zero inv
Although a modulation or the like can be used, a random signal as shown in FIG. 6 is recorded with the shortest mark length being 0.5 μm or less. In this evaluation, the shortest mark length was 0.
The thickness is preferably about 2 μm or more. Note that it is not necessary to satisfy the above expression under all evaluation conditions, and it is sufficient that the above expression is satisfied under one evaluation condition.

As an example, a random signal of the EFM plus modulation method is recorded with a plurality of mark lengths having a minimum mark length of 0.4 μm. The modulation degree is obtained by standardizing the signal amplitude of the longest mark of the modulation method by the top signal strength. FIG. 6 shows a waveform of a DC reproduction signal (reproduction signal including a DC component) when a random signal modulated by EFM plus is recorded and reproduced. The degree of modulation is defined as the ratio I ₁₄ / I _top between the signal intensity I _{top at} the top of the 14T mark and the signal amplitude I ₁₄ . If the degree of modulation does not change, it can be determined that the amorphous mark size is sufficiently stable. If the degree of modulation of the random signal recorded before the acceleration test maintains 90% or more of the initial value after the acceleration test, it can be estimated that crystal nucleation is not substantially involved.

In the recording layer of the present invention, the crystal growth from the peripheral crystal part is likely to occur in a high temperature region just below the melting point. From which crystal growth can occur. Therefore, if the cooling rate after melting is slow and does not reach the critical cooling rate required for solidification as amorphous, the entire molten region is recrystallized almost instantaneously.

This can be confirmed by the following experiment. Record
Polycarbonate 0.6mm thick with grooves for guiding reproduction light
(ZnS) on the substrate₈₀(SiO_Two)₂₀First protection
The layer is 68 nm thick, Ge_0.05Sb_0.71Te _0.24The recording layer
18 nm thick, (ZnS)₈₀(SiO_Two)₂₀Second protective layer
With a film thickness of 20 nm and Al_0.995Ta_0.005Reflective layer thickness 2
50 nm, provided in this order, and a UV-curable resin protective layer
Was provided in a thickness of 4 μm. Put these two sheets on the side with the recording layer
Put it inside and glue it with hot melt adhesive to optical recording medium
did. The composition of this recording layer is over at a linear velocity of about 7 m / s or more.
Sb / Te ≒ 3 was set to enable writing. In this medium,
Elliptical laser light with a major axis of about 100 μm and a minor axis of about 1.5 μm
Was melted and recrystallized by scanning in the short axis direction to initialize.

The medium has a wavelength of 637 nm and NA = 0.6.
The focused light of No. 3 was irradiated at a linear velocity of 7 m / s according to the guide groove. After irradiating a recording light with a recording power Pw of 10 mW in a DC manner, the power was rapidly dropped to 1 mW. That is,
The recording light was substantially blocked. The beam diameter is about 0.9
μm, which corresponds to a region where the energy intensity of the Gaussian beam is 1 / e ² or more of the peak intensity.

FIG. 2 shows the change in reflectance before and after the recording light is blocked. As shown in the lower part of FIG. 2, the recording light was shut off as time passed. The recording light is irradiated continuously, that is, in a DC manner on the left side in the lower part of FIG. 2, and is blocked on the right side. When the same area was scanned with reproduction light having a reproduction power of 1.0 mW, a reproduction waveform as shown in the upper part of FIG. 2 was obtained.
This corresponds to a change in reflectance.

The reflectance decreases near the moment when the recording light is momentarily cut off, and before and after that, the reflectance is almost the same.
TEM observation confirmed that the reflectance-reduced portion was amorphous, and before and after it was crystalline. That is, as long as the recording light is continuously irradiated, the melted portion is recrystallized, and only the melted region near the portion where the recording light is blocked becomes amorphous.

This is because when the recording light is continuously irradiated, the cooling rate of the recording layer is suppressed by the residual heat from the subsequent portion, and the critical cooling rate required for forming an amorphous phase cannot be obtained. This is because, by temporarily blocking the recording light, the residual heat from the subsequent portion can be blocked, and the cooling rate can be increased. When the recording power Pw was 7 mW or more, an amorphous mark was formed by blocking recording light.

As a result of the study, the medium of the present invention is substantially recrystallized when continuously irradiated with a recording light having a recording power Pw sufficient to melt the recording layer at a constant linear velocity, and the recording layer is fixed at a constant linear velocity. It was found that an amorphous mark was formed by irradiating a recording light with a power of almost 0 following a recording light with a recording power Pw sufficient to melt the mark. When the power is almost 0, it is not necessary to be exactly 0, and 0 ≦ Pb ≦ 0.2Pw
Bias power Pb, more preferably 0 ≦ Pb ≦
That is, the bias power Pb is set to 0.1 Pw.

In the present invention, recrystallization during resolidification of the molten portion occurs almost exclusively by crystal growth from the surrounding solid phase crystal portion. Therefore, since the recrystallized portion is not formed at the center of the amorphous mark, a smooth and continuous mark edge is formed. Heretofore, it has been considered that such a material which is recrystallized remarkably is not suitable for the recording layer for recording the mark length. This is because if the recording light is irradiated for a long time to form a long mark, most of the molten region is crystallized.

However, according to the study of the present inventors, in high-density recording with a minimum mark length of less than 0.5 μm,
Good jitter can be obtained by actively using the competition process between the amorphization of the molten region and the recrystallization from the boundary of the surrounding solid phase crystal part. For this reason, it has been found that a pulse division method in which a recording power Pw application section and its cutoff section, that is, a bias power Pb application section are combined, is extremely effective for forming a mark having a length of nT as described later.

When recording is performed by the pulse division method, as shown in FIG. 1, an amorphous mark is formed by connecting arrow-shaped (or crescent-shaped) amorphous portions. The shape of the beginning of the mark is determined only by the shape of the beginning of the leading arrow feather-shaped amorphous portion, and the shape of the rear end of the mark is determined only by the shape of the trailing end of the trailing arrow-shaped amorphous portion. Usually, the starting shape of the amorphous portion is smooth, so that the mark starting shape is also smooth. This is because the cooling rate is kept sufficiently high due to the escape of heat to the front, so that the shape substantially reflects the shape of the tip of the melting region and is therefore governed by the rise time of the recording pulse. The rising of the recording pulse, that is, the rise of the Pw application section may be 2 to 3 nanoseconds or less.

On the other hand, the shape of the rear end of the amorphous portion is determined by the cooling rate determined by the fall time of the recording pulse and the size of the recrystallization region that advances from the periphery, particularly the crystal portion at the rear end. In order to sufficiently increase the cooling rate, the fall of the Pw application section is desirably 2 to 3 nanoseconds or less. The size of the recrystallization region can be accurately controlled by the off-pulse, that is, the length of the Pb application section. Further, by applying the above-described super-quenching structure as a layer structure, the cooling rate of the recording layer is made as steep as possible, and the spatial distribution of the cooling rate is made sharp near the rear end of the mark, so that the position of the mark end is changed. It is also important that there is no fluctuation

The inventors of the present invention have conducted intensive studies on an optical recording medium capable of recording short marks at high speed and having excellent stability over time of the recorded marks. As a result, Ge was added near the eutectic composition of Sb _0.7 Te _0.3. The specific composition was found to be particularly excellent, and an optical recording medium excellent in other characteristics was obtained by appropriately selecting the layer constitution. That is, Sb _0.7 Te
Focusing on an unconventional ternary alloy obtained by adding excess Sb and Ge to _0.3 , the suitability for high-density mark length modulation recording was examined. As a result, in the GeSbTe ternary phase diagram shown in FIG. 3, a medium surrounded by four straight lines A, B, C, and D using a recording layer composition having a very limited Ge—Sb—Te ratio is In high-density mark length modulation recording, it has been found that repetitive overwrite durability and temporal stability are particularly excellent.

That is, in the GeSbTe ternary phase diagram, a straight line A connecting the (Sb _0.7 Te _0.3 ) and Ge, (Ge
A straight line B connecting _0.03 Sb _0.68 Te _0.29 ) and (Sb _0.95 Ge _0.05 ), (Sb _0.9 Ge _0.1 ) and (Te _0.9 Ge _0.1 )
And a thin film mainly composed of a GeSbTe alloy having a composition of a region surrounded by four straight lines (not including the boundary line) of a straight line C connecting (Sb _0.8 Te _0.2 ) and a straight line D connecting Ge. The recording layer. By using a layer configuration described later for this recording layer, a medium very suitable for high-density mark length modulation recording with a minimum mark length of 0.5 μm or less can be obtained. Then, it is possible to obtain the same recording density as DVD and excellent reproduction compatibility with DVD.

In addition, repeated overwrite durability,
A wide margin for obtaining good jitter with respect to fluctuations in recording power and erasing power can be secured. Within this composition range, the larger the amount of Sb from y = 0.7 in the Sb _y Te _1-y alloy, increasing excess amount of Sb, it is possible to overwrite at a crystallization rate is high a high linear velocity.

More specifically, in EFM plus modulation recording (mark length modulation recording of 8-16 modulation), the length of the shortest mark 3T mark is set to 0.4 μm or 0.1 μm.
Good jitter can be obtained even when reduced to about 35 μm. In addition, a sufficient servo signal is obtained, and tracking servo can be applied with an existing read-only DVD drive. Further, overwriting is possible at any one of linear velocities of 1 to 10 m / s.

As a result, it is possible to obtain a rewritable DVD having the same capacity as the read-only DVD and having almost the same playback compatibility. If the excess Sb amount is controlled, the above-described high quality and high density overwriting can be performed at a high linear velocity of 8 m / s or more. Also, by changing the recording pulse division method (pulse strategy) according to the linear velocity as described later, good overwriting can be performed in a wide linear velocity range including at least 3 to 8 m / s.

The present composition will be described in detail below.
In a composition near the eutectic point of Sb _0.7 Te _0.3 where the amount of Ge added is 10 atomic% or less, the crystallization rate tends to increase as the Sb / Te ratio increases. This excess of Sb from Sb _0.7 Te _{0. 3} is because act as crystal nuclei in the re-crystallization process precipitate as Sb clusters. And Sb _0.7 T
If there is no excess of Sb from e _0.3 is is insufficient substantially overwriting impossible erasing performance. There is also a problem that initialization is difficult and productivity is very poor because nucleation hardly occurs during initialization (straight line A).

On the other hand, Sb _0.7 Te _0.3 eutectic binary alloy
As the amount of b increases, the crystallization speed decreases, but the crystallization temperature also decreases, and the aging stability of the amorphous mark is impaired. Further, it is not suitable for recording at a low linear velocity of about 3 m / s, and the formed amorphous mark disappears by short-time irradiation with reproduction light (about 1 mW of laser power). Therefore, a straight line D connecting (Sb _0.8 Te _0.2 ) and Ge
Excess Sb should not be included.

The excess Sb defined by the straight lines A and D
In the range of the amount, if the binary SbTe is used, the crystallization temperature is low and the crystal nucleus of excess Sb is present, so that the amorphous mark becomes too unstable. Therefore, Ge is added as the excess Sb amount increases. I do. Ge nucleation is almost completely suppressed by the four-coordinate bond of Ge. As a result, the crystallization temperature rises and the stability over time increases. (Ge _0.03 Sb _0.68 Te _0.29 )
A straight line B that connects (Sb _0.95 Ge _0.05 ) defines this condition. More preferably, (Ge _0.03 Sb _0.68 Te
_0.29 ) and (Sb _0.9 Ge _0.1 ).

Further, when the Ge content is 10 atomic% or more, the jitter at the time of recording the mark length deteriorates, and a high melting point Ge compound, particularly a Ge compound, is obtained by repeated overwriting.
Te is easily segregated. Further, it is not preferable because crystallization of the amorphous film immediately after film formation becomes extremely difficult (straight line C). In order to reduce jitter, Ge is preferably set to 7.5 atomic% or less.

It is to be noted that the linear velocity is not less than 3 m / s.
To record, the recording layer should be Ge_x(Sb _yTe_1-y)_1-xCombination
Thin film containing gold as a main component (0.04 ≦ x <0.10, 0.
It is preferable that 72 ≦ y <0.8). That is, the line
For recording at a speed of 3 m / s or more, the Sb amount is increased,
_yTe_1-yIt is preferable that y ≧ 0.72 in the alloy
No. However, by increasing the amount of Sb, the amorphous mark
Is slightly deteriorated, and to compensate for this, x ≧ 0.
It is preferable to increase 04 and Ge. Furthermore, linear velocity
To overwrite at a speed of 7 m / s or more, the recording layer must be G
e_x(Sb_yTe_1-y)_1-xAlloy-based thin film
(0.045 ≦ x ≦ 0.075, 0.74 ≦ y <0.
8) is preferable. That is, linear velocity of 7 m / s or less
In the above record, the Sb amount was further increased,_yTe
_1-yIt is preferable that y ≧ 0.74 in the alloy. This
In order to increase the stability of the amorphous mark, the Ge amount is
Let x ≧ 0.045. On the other hand, jitter deteriorates at high linear velocity
In order to compensate for this, the Ge amount is set to x ≦ 0.07
5 is assumed.

Conventionally, there has been reported a ternary composition of GeSbTe or a composition of a recording layer containing an additional element based on the ternary composition (JP-A-61-2).
No. 58787, No. 62-53886, No. 62
JP-152786, JP-A-1-63195,
Nos. 1-211249 and 1-277338). However, any of the compositions described in these publications shows that Sb is obtained from the straight line A connecting (Sb _0.7 Te _0.3 ) and Ge.
This is a poor composition, which is different from the composition range of the present invention. Rather, they are mainly based on the Sb ₂ Te ₃ metal compound composition. In the GeTe-Sb ₂ Te ₃ pseudo binary alloy system, contrary to the present invention, excessive Sb has the effect of slowing down the crystallization speed. , the straight line of GeTe-Sb ₂ Te _3, especially Ge ₂ Sb ₂ Te ₅ composition, it is rather detrimental to incorporate excess Sb. Sb containing excess Sb
A composition in which a third element containing Ge is selectively added in the vicinity of _0.7 Te _0.3 is disclosed in JP-A-1-100745 (FIG. 4).
(A) Composition range α) and JP-A No. 1-303643 (FIG. 4A).

[0054] However, JP-A-1-100745, in Sb _1-x Te x is a matrix composition 0.1
It is extremely wide as 0 ≦ x ≦ 0.80, and Sb _0.7 Te
_The idea of the present application that excellent overwrite durability and stability over time in high-density recording is not observed by using only the region in which Sb is excessive than _0.3 . JP-A-1-30
No. 3643 discloses S.D. in high-density recording as in the present application.
No mention is made of the adverse effect that the excess of b beyond the straight line D will impair the stability over time of the amorphous mark. In addition, none of the publications mentions the harmful effects of excessive inclusion of Ge beyond the straight line C.

As shown in FIG. 4B, the composition partially overlapping the composition of the recording layer of the present invention is disclosed in
JP-A-115885 (composition range γ),
No. 42 (composition range δ), JP-A-3-71887 (composition range ε) and JP-A-4-28587 (composition range η). JP-A-1-115885
In this publication, Au and Pd are added with the composition range γ as a base material, but for the purpose of low-density recording, are substantially distinguished from the composition of the present invention by a straight line A and a straight line B. The composition of this publication is suitable for recording at a low density corresponding to a mark length of about 1.1 μm (linear velocity of 4 m / s, frequency of 1.75 MHz, square wave of 50% duty) and DC erasing. It is considered that a suitable composition is different from the composition of the present invention intended for high-density recording including a short mark.

The composition range δ in Japanese Patent Application Laid-Open No. 1-251342 is a very Ge-rich GeSb mainly composed of a system obtained by adding about 10 atomic% or more of Ge to Sb _0.7 Te _0.3 eutectic.
It is a Te system and is substantially distinguished from the composition of the present invention by a straight line C. In the composition range δ, when the composition contains more than 10 atomic% of Ge, the crystallization rate is low as described above, and particularly, the initialization operation for crystallizing the recording layer after film formation is difficult, so that the productivity is low. However, there is a serious problem that it is not practical for practical use. In this publication, Au and Pd serving as crystal nuclei are separately added in order to overcome the problem of the crystallization speed. However, in a region where Ge is smaller than the straight line C as in the present invention, such a necessity is required. There is no. Further, in this publication, it is described that if the amount of Ge is less than 10 atomic%, a sufficient change in the amount of light cannot be obtained between the recorded portion and the non-recorded portion. By devising the layer structure including the light emitting element, a very large change in the reflected light amount of 60% or more in the degree of modulation can be obtained. JP-A-3-71
No. 887, the composition range ε is intended for low density recording,
It is substantially distinguished from the composition of the present invention by a straight line C. In particular, the idea of the present application that the use of the composition range of the present invention is excellent in repeated overwrite durability and stability over time in high-density recording is not seen. JP-A-4-2858
No. 7, the composition range η is extremely Sb-rich and Ge
It contains a rich composition and is substantially distinguished from the composition of the present invention by a straight line D. As described above, none of the above publications clarifies the technical problem relating to high-density mark length modulation recording in which the shortest mark length is 0.5 μm or less, which is the object of the present invention. There is no disclosure of the selection of the optimum composition and the improvement of the layer structure and the recording method.

Next, the layer structure of the optical information recording medium of the present invention will be described. The medium of the present invention has a combination of the recording layer having the above-described composition and the following layer configuration. A medium capable of overwriting over a wide linear velocity range, preferably covering 1 m / s to 10 m / s, can be realized. Then, reproduction compatibility with a so-called DVD can be maintained. The phase change recording layer has at least one of the upper and lower layers covered with a protective layer.

Further, as shown in FIG.
It has the structure of the first protective layer 2 / recording layer 3 / second protective layer 4 / reflective layer 5, and the surface thereof is covered with ultraviolet or thermosetting resin (protective coat layer 6). The order of each layer as shown in FIG. 5A is suitable when the recording layer is irradiated with a focused light beam for recording / reproducing through the transparent substrate. Or,
The order of the above layers is reversed, and as shown in FIG. 5 (b), the substrate 1 / the reflective layer 5 / the second protective layer 4 / the recording layer 3 / the first protective layer 2
, And the layers may be stacked in this order. This layer configuration is
This is suitable when a focused light beam is incident from the first protective layer side. Such a configuration is useful when the objective numerical aperture NA is 0.7 or more and it is necessary to shorten the distance between the recording layer and the objective lens.

With the configuration shown in FIG. 5A, a transparent resin such as polycarbonate, acrylic, or polyolefin, or transparent glass can be used for the substrate. Among them, polycarbonate resin is the most preferable because it has the track record of being most widely used in CDs and is inexpensive. In the configuration shown in FIG. 5B, resin or glass can be used in the same manner, but the substrate itself does not need to be transparent. Rather, it is preferable to use glass or an aluminum alloy in order to increase flatness and rigidity. is there.
The substrate is provided with a groove having a pitch of 0.8 μm or less for guiding the recording / reproducing light, but this groove is not necessarily required to be a geometrically trapezoidal groove. A groove may be formed optically by forming something like a waveguide.

In the layer structure shown in FIG. 5A, the first protective layer 2 is provided on the substrate surface and the second protective layer 4 is provided on the recording layer 3 in order to prevent deformation due to high temperature during recording. Provided. The second protective layer 4 also has a function of preventing mutual diffusion between the recording layer 3 and the reflective layer 5 and suppressing heat deformation to the reflective layer 5 while suppressing deformation of the recording layer. Also in FIG. 5B, the second protective layer 4 is the recording layer 3 when viewed from the focused light beam incident side.
It has a function of preventing mutual diffusion between the film and the reflective layer 5, heat radiation, and preventing deformation of the recording layer. The first protective layer in FIG.
It has functions of preventing deformation of the recording layer, preventing direct contact between the recording layer and air (prevention of oxidation contamination, etc.), and preventing damage due to direct contact with the optical pickup.

A protective layer may be further provided between the reflective layer and the substrate. For example, heat damage to the resin substrate can be prevented. In the configuration shown in FIG.
It is desirable to provide a harder dielectric or amorphous carbon protective film, or an ultraviolet or thermosetting resin layer further outside the first protective layer 2. Alternatively, it is also possible to attach a transparent thin plate having a thickness of about 0.05 to 0.6 mm, and to allow a focused light beam to enter through this thin plate.

Further, in a medium such as a DVD,
The medium shown in FIG. 5A has a structure in which the recording layer surface is on the inside and the medium is bonded with an adhesive. On the other hand, in the medium shown in FIG. 5B, the recording layers are bonded with the recording layer surface outside. Further FIG.
In the medium (b), a tracking groove may be formed on both surfaces of a single substrate by injection molding, and a multilayer film may be formed on both surfaces by sputtering. The recording layer 3, the protective layers 2, 4, and the reflective layer 5 are 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.

The material of the protective layers 2 and 4 is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like. Generally, oxides, sulfides, nitrides, carbides, Ca, and the like of metals and semiconductors having high transparency and high melting point are used.
Fluorides such as Mg and Li can be used. These oxides, sulfides, nitrides, carbides and fluorides do not necessarily have to have a stoichiometric composition, and it is effective to control the composition for controlling the refractive index and the like, or to use a mixture of them. is there.

The composition ratio and the mixing ratio of the protective layers 2 and 4 may be changed in the thickness direction. Further, each of the protective layers 2 and 4 may be composed of a plurality of films. Each membrane depends on the required characteristics,
Materials, composition ratios, and mixing ratios can be varied. 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.

[0065]

Ρ = Σm _i ρ _i (1) m _i : molar concentration of each component i ρ _i : single bulk density

The recording layer 3 of the medium of the present invention is a phase change type recording layer, and its thickness is generally preferably in the range of 5 nm to 100 nm. If the thickness of the recording layer 3 is less than 5 nm, it is difficult to obtain a sufficient contrast and the crystallization speed tends to be slow, so that erasing in a short time tends to be difficult.
On the other hand, if it exceeds 100 nm, it is still difficult to obtain optical contrast, and cracks are likely to occur. Further, for high-density recording in which the contrast is required to be compatible with a read-only disc such as a DVD and the shortest mark length is 0.5 μm or less, 5 nm is required.
It is preferably at least 25 nm. If the thickness is less than 5 nm, the reflectance is too low, and the influence of a non-uniform composition and a sparse film in the initial stage of film growth tends to appear, which is not preferable.

On the other hand, if the thickness is more than 25 nm, the heat capacity becomes large, the recording sensitivity becomes poor, and the crystal growth becomes three-dimensional, so that the edges of the amorphous marks tend to be disturbed and the jitter tends to be high. Further, the volume change due to the phase change of the recording layer becomes remarkable, and the overwrite durability is repeatedly deteriorated. From the viewpoint of mark end jitter and repetitive overwrite durability, it is more preferable to set the thickness to 20 nm or less. Further, the density of the recording layer is desirably 80% or more, more preferably 90% or more of the bulk density.
Here, the bulk density can be measured, of course, by preparing an alloy lump, but in the above equation (1),
An approximate value can be obtained by replacing the molar concentration of each component with the atomic% of each element and replacing the bulk density with the molecular weight of each element.

In the case of the sputter film forming method, the density of the recording layer is determined by lowering the pressure of a sputter gas (a rare gas such as Ar) at the time of film formation or by disposing a substrate close to the front of the target. It is necessary to increase the amount of high energy Ar irradiated to the layer. The high-energy Ar is one in which Ar ions applied to the target for sputtering are partially repelled and reach the substrate side, or Ar ions in the plasma.
Either ions are accelerated by the sheath voltage on the entire surface of the substrate and reach the substrate. Such an irradiation effect of a high-energy rare gas is called an atomic peening effect. Ar is mixed into a sputtered film due to an atomic peening effect in sputtering with a generally used Ar gas. Atomi depends on the amount of Ar in the film.
The c-peening 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, when the amount of Ar is large, the irradiation of high-energy Ar is intense and the density becomes high, but the A taken in the film
r precipitates as voids during repeated overwriting, deteriorating the durability of repetition. An appropriate amount of Ar in the recording layer film is 0.1 atomic% or more and 1.5 atomic% or less. 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.

In the present invention, the recording layer comprises a thin film mainly composed of a GeSbTe alloy having the above composition. That is, the ratio of the amounts of the respective elements Ge, Sb, and Te in the recording layer may be within the above-described composition range. If necessary, other elements may be added to the recording layer up to a total of about 10 atomic%. Good.
The optical constant of the recording layer can be finely adjusted by further adding at least one element selected from O, N, and S to the recording layer in an amount of 0.1 to 5 atomic%. However, adding more than 5 atomic% is not preferable because it lowers the crystallization speed and deteriorates the erasing performance.

In order to increase the stability over time without lowering the crystallization speed during overwriting, V, Nb, T
at least one of a, Cr, Co, Pt and Zr is 8
It is preferable to add at most atomic%. More preferably,
0.1 atomic% or more and 5 atomic% or less are added. The total amount of these additional elements and Ge added to SbTe is 1 in total.
It is desirable that the content be 5 atomic% or less. Excessive inclusion will induce phase separation other than Sb. In particular, when the Ge content is 3 atomic% or more and 5 atomic% or less, the addition effect is large. To improve the aging stability and fine-tune the refractive index,
It is preferable to add at least one of i, Sn, and Pb to 5 atomic% or less. The total content of these additional elements and Ge is preferably 15 atomic% or less. These elements are Ge
Has the same four-coordinate network as.

The addition of 8 atomic% or less of Al, Ga, and In has the effect of increasing the crystallization temperature and at the same time reducing jitter and improving the recording sensitivity. However, segregation is likely to occur. It is preferably at most atomic%. Further, the content together with Ge is desirably 15 atomic% or less, preferably 13% or less. Addition of 8 atomic% or less of Ag is also effective in improving the recording sensitivity, and the effect is particularly remarkable when used when the Ge atomic weight exceeds 5 atomic%. However, addition exceeding 8 atomic% is not preferable because it increases jitter and impairs the stability of the amorphous mark.
If it exceeds atomic%, segregation tends to occur, which is not preferable.
The most preferable Ag content is 5 atomic% or less.

The state of the recording layer 3 of the recording medium of the present invention after film formation is usually amorphous. Therefore, after film formation,
It is necessary to crystallize the entire recording layer to be in an initialized state (unrecorded state). The initialization method is Sb _0.7
The alloy containing excessive Sb to Te _0.3, but it is possible also initialized by annealing in a solid phase, the composition further comprising Ge, to crystallize slowly cooled during resolidification was temporarily melt the recording layer melted Initialization by recrystallization is desirable. This recording layer has almost no crystal growth nuclei immediately after film formation, and it is difficult to crystallize in the solid phase. It seems that recrystallization proceeds at a high speed mainly due to crystal growth.

In the recording layer of the present invention, the crystal formed by melting and recrystallization and the crystal formed by annealing in a solid phase have different reflectivities. And
At the time of actual overwrite recording, since the erased portion becomes a crystal formed by melt recrystallization, it is preferable that initialization is also performed by melt recrystallization. At this time, the recording layer is locally melted and is limited to a short time of about 1 millisecond or less. If the melting region is wide or the melting time or the cooling time is too long, each layer is destroyed by heat or the surface of the plastic substrate is deformed. In order to provide such a heat history, a high-power semiconductor laser beam having a wavelength of about 600 to 1000 nm is irradiated with a long axis of 100 to 300 μm and a short axis of 1 to 300 μm.
Focused on 3 μm and irradiated, with the short axis direction as the scanning axis, 1
It is desirable to scan at a linear velocity of 10 to 10 m / s. Even with the same focused light, if it is close to a circular shape, the melting region is too wide and re-amorphization is likely to occur, and the multilayer structure and the substrate are greatly damaged, which is not preferable. The fact that the initialization was performed by melt recrystallization can be confirmed as follows. That is, the medium after the initialization is irradiated with a recording light of a recording power Pw focused on a spot diameter smaller than about 1.5 μm and having a recording power Pw for melting the recording layer, at a constant linear velocity in a DC manner. If there is a guide groove, the tracking servo and the focus servo are performed on the track formed between the grooves or between the grooves.

Thereafter, the erasing power Pe is recorded on the same track.
If the reflectance in the erased state obtained by irradiating the erasing light of (≦ Pw) in a DC manner is almost the same as the reflectance in the completely unrecorded initial state, the initialized state is confirmed to be the crystalline state upon melting. it can. The reason for this is that the recording layer is once melted by the irradiation of the recording light, and is completely recrystallized by the irradiation of the erasing light. It is because it is in a state of being transformed. It should be noted that the reflectance of the initialized state R _ini and the reflectance of the melted and recrystallized state R _cry are substantially the same as (R _ini −R
_cry ) / {( _Rini + _Rcry ) / 2} means that the difference between the two reflectances is 20% or less. Normally, only by solid-phase crystallization such as annealing, the reflectance difference is larger than 20%.

Next, the layers other than the recording layer will be described. The layer configuration of the present invention belongs to a kind of layer configuration called a quenching structure. The quenching structure employs a layer configuration that promotes heat radiation and increases the cooling rate during resolidification of the recording layer, thereby avoiding the problem of recrystallization when forming an amorphous mark and achieving high crystallization by high-speed crystallization. Achieve an erasing ratio. Therefore, the thickness of the second protective layer is set to 5 nm or more and 30 nm or less. If the thickness is less than 5 nm, the recording layer is easily broken by deformation or the like when the recording layer is melted, and the power required for recording becomes unnecessarily large because the heat radiation effect is too large.

In the present invention, the thickness of the second protective layer greatly affects the durability in repeated overwriting, and is particularly important in suppressing the deterioration of jitter. Thickness 30nm
If it is thicker, at the time of recording, the recording side of the second protective layer
The temperature difference between the reflection layer side and the reflection layer side increases, and the protection layer itself tends to be asymmetrically deformed due to the difference in thermal expansion between both sides of the protection layer. This repetition is not preferable because it causes microscopic plastic deformation to accumulate inside the protective layer and increases noise. By using the recording layer of the present invention, low jitter can be realized in high-density recording with a minimum mark length of 0.5 μm or less. However, according to the study of the present inventors, a short-wavelength laser In the case of using a diode (for example, a wavelength of 700 nm or less), further attention must be paid to the layer structure of the quenching structure. In particular, in the study of one-beam overwrite characteristics using a small focused light beam having a wavelength of 500 nm or less and a numerical aperture NA of 0.55 or more, flattening the temperature distribution in the mark width direction requires a high erasing ratio and erasing. It turned out to be important for widening the power margin.

This tendency is due to the fact that the wavelengths of 630 to 680 nm, N
The same applies to a DVD-compatible optical system using an optical system with A = about 0.6. In high density mark length modulation recording using such an optical system, a material having low thermal conductivity is used as the second protective layer. Preferably, the thickness is 10 nm or more and 25 nm or less. In each case,
The erasing ratio and the erasing power margin can be improved by using a material having particularly high thermal conductivity for the reflective layer 5 provided thereon. According to the study, over a wide erase power range,
In order to exhibit good erasing characteristics of the recording layer of the present invention,
It is preferable to use a layer configuration that can flatten as much as possible the temperature distribution in the film surface direction (perpendicular to the recording beam scanning direction) as well as the temperature distribution and time change in the film thickness direction.

By appropriately designing the layer structure of the medium, the present inventors can flatten the temperature distribution in the cross-track direction in the medium, so that the medium is not melted and re-amorphized. An attempt was made to increase the width that can be recrystallized, and to increase the erasing rate and erasing power margin. On the other hand, it was found that by promoting heat radiation from the recording layer to the reflection layer having extremely high thermal conductivity through the very thin second protective layer having a low thermal conductivity, the temperature distribution in the recording layer became flat. . Even if the thermal conductivity of the second protective layer is increased, the heat radiation effect is promoted. However, if the heat radiation is promoted too much, the irradiation power required for recording increases, that is, the recording sensitivity is significantly reduced.

In the present invention, a thin second conductive material having a low thermal conductivity is used.
It is preferable to use a protective layer. Low thermal conductivity, thin second
By using the protective layer, the heat conduction from the recording layer to the reflective layer is given a time delay from several nsec to several tens of nsec at the start of the recording power irradiation, and then the heat radiation to the reflective layer is promoted. As a result, the recording sensitivity is not unnecessarily lowered by heat radiation. Conventionally known SiO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , AlN, Si
A protective layer material containing N as a main component is not preferable as the second protective layer 4 of the medium of the present invention because its own thermal conductivity is too high. As described above, the thermal conductivity of the metal oxide or nitride is higher by one digit or more than that of the following protective layer used in the protective layer of the present invention even in the same thin film state.

On the other hand, heat dissipation in the reflective layer can be achieved by increasing the thickness of the reflective layer, but the thickness of the reflective layer is 300 n
If it exceeds m, the heat conduction in the film thickness direction becomes more remarkable than in the film surface direction, and the effect of improving the temperature distribution in the film surface direction cannot be obtained. In addition, the heat capacity of the reflection layer itself increases, and the reflection layer,
As a result, it takes a long time to cool the recording layer, and the formation of an amorphous mark is hindered. Most preferably, a reflective layer having a high thermal conductivity is provided thinly to selectively promote heat radiation in the lateral direction. The quenching structure conventionally used focuses only on one-dimensional heat dissipation in the film thickness direction, and is intended only to quickly release heat from the recording layer to the reflective layer.
Sufficient attention has not been paid to the flattening of the temperature distribution in the plane direction.

Incidentally, the so-called “ultra-quenching structure in consideration of the heat conduction delay effect in the second protective layer” of the present invention, when applied to the recording layer according to the present invention, is a conventional GeTe—Sb ₂ Te _3.
It is more effective than the recording layer. This is because, in the recording layer of the present invention, the crystal growth at the time of resolidification in the vicinity of Tm is rate-determining of recrystallization. In order to increase the instantaneous cooling rate near Tm to the utmost limit and to make the formation of the amorphous marks and their edges reliable and clear, an ultra-quenched structure is effective, and the temperature distribution in the film surface direction is effective. This is because, by the flattening, the data which could originally be erased at a high speed near Tm can be reliably erased by recrystallization up to a higher erasing power.

In the present invention, it is desirable that the material of the second protective layer has low thermal conductivity, but the standard is 1 × 10
⁻³ pJ / (μm · K · nsec). However, it is difficult to directly measure the thermal conductivity of such a low-thermal-conductivity material in a thin film state, and a guide can be obtained from a thermal simulation and an actual recording sensitivity measurement result. As a material of the second protective layer having a low thermal conductivity that provides a favorable result, at least one of ZnS, ZnO, TaS ₂ or a rare earth sulfide is used in an amount of 50 mol% or more.
0 mol% or less and melting point or decomposition point is 1000
A composite dielectric containing a heat-resistant compound having a temperature of not less than ° C is desirable.

More specifically, a composite dielectric containing 60 mol% or more and 90 mol% or less of rare earth sulfides such as La, Ce, Nd, and Y is desirable. Alternatively, the composition range of ZnS, ZnO or rare earth sulfide is set to 70 to 90 mol%.
It is desirable that Heat-resistant compound materials having a melting point or a decomposition point of 1000 ° C. or higher to be mixed with these include Mg, Ca, Sr, Y, La, Ce, Ho, Er,
Yb, Ti, Zr, Hf, V, Nb, Ta, Zn, A
oxides, nitrides, carbides and C such as l, Si, Ge, Pb, etc.
A fluoride such as a, Mg, and Li can be used. Particularly, materials to be mixed with ZnO include Y, La, C
A rare earth sulfide such as e or Nd or a mixture of a sulfide and an oxide is desirable. The thickness of the second protective layer is 30
If it is thicker than 30 nm, a sufficient flattening effect of the temperature distribution in the mark width direction cannot be obtained. Preferably, the thickness is 25 nm or less. If it is less than 5 nm, the effect of delaying heat conduction in the second protective layer portion is insufficient, and the recording sensitivity is significantly reduced, which is not preferable. The thickness of the second protective layer 4 is 15 nm to 25 when the wavelength of the recording laser beam is 600 to 700 nm.
nm is preferable, and 5-2 when the wavelength is 350 to 600 nm.
0 nm is preferable, and more preferably 5 to 15 nm.

In the present invention, a very high thermal conductivity of 3
It is characterized by using a thin reflective layer 5 of not more than 00 nm to promote the heat radiation effect in the lateral direction. In general, the thermal conductivity of a thin film is significantly different from the thermal conductivity in a bulk state, and is generally small. In particular, in the case of a thin film having a thickness of less than 40 nm, the thermal conductivity may be reduced by one digit or more due to the effect of the island structure at the initial stage of growth, which is not preferable. Further, the crystallinity and the amount of impurities vary depending on the film forming conditions, and this causes a difference in thermal conductivity even with the same composition.

In the present invention, the heat conductivity of the reflective layer can be directly measured in order to define a high thermal conductivity reflective layer exhibiting good characteristics. Can be estimated. This is because in a material such as a metal film in which electrons mainly perform heat or electric conduction, there is a good proportional relationship between the thermal conductivity and the electric conductivity. The electrical resistance of a thin film is represented by a resistivity value standardized by its film thickness or the area of a measurement region. The volume resistivity and the sheet resistivity can be measured by a normal four-probe method, and are defined by JIS K7194. According to this method, data that is much simpler and has better reproducibility than actual measurement of the thermal conductivity itself of a thin film can be obtained. In the present invention, the reflective layer preferably has a volume resistivity of 20 nΩ · m to 150 nΩ · m, more preferably 20 nΩ · m to 100 nΩ · m. Materials having a volume resistivity of less than 20 nΩ · m are substantially difficult to obtain in a thin film state. Even when the volume resistivity is larger than 150 nΩ · m, the sheet resistivity can be reduced by forming a thick film exceeding 300 nm, for example.
According to the study of the present inventors, a sufficient heat radiation effect was not obtained even if only the sheet resistivity was reduced with such a high volume resistivity material. It is considered that a thick film increases the heat capacity per unit area. Moreover, such a thick film is not preferable from the viewpoint of manufacturing cost because it takes a long time to form the film and increases the material cost. Further, the microscopic flatness of the film surface is deteriorated. Preferably, a low volume resistivity material is used so that a sheet resistivity of 0.2 to 0.9 Ω / □ is obtained at a thickness of 300 nm or less. 0.5Ω / □ is most preferred.

Materials suitable for the present invention are as follows. For example, it is an Al-Mg-Si alloy containing 0.3 wt% to 0.8 wt% of Si and 0.3 wt% to 1.2 wt% of Mg. In addition, Ta, T
i, Co, Cr, Si, Sc, Hf, Pd, Pt, M
g, Zr, Mo, or Mn in an amount of 0.2 atomic% or more and 2 atomic%
The Al alloy containing below has an increase in volume resistivity in proportion to the concentration of the added element, and has improved hillock resistance, durability,
It can be used in consideration of volume resistivity, film forming speed, and the like.
Regarding the Al alloy, if the amount of the added impurity is less than 0.2 atomic%, the hillock resistance is often insufficient, depending on the film formation conditions. On the other hand, if it is more than 2 atomic%, it is difficult to obtain the above low resistivity. When importance is placed on the stability over time, Ta is preferred as an additive component. In particular, for the upper protective layer 4 containing ZnS as a main component, an AlTa alloy containing 0.5 atomic% or more and 0.8 atomic% or less of Ta has corrosion resistance,
It is desirable as a reflective layer that satisfies all of adhesion and high thermal conductivity in a well-balanced manner. Further, in the case of Ta, addition of only 0.5 atomic% compared to pure Al or Al-Mg-Si alloy,
A favorable effect in production that the film formation rate during sputtering is increased by 30 to 40% is obtained. When the above-mentioned Al alloy is used as the reflective layer, a preferable film thickness is 150 nm or more and 300 nm or less. If it is less than 150 nm, the heat radiation effect is insufficient even with pure Al. When the thickness exceeds 300 nm, heat escapes in the vertical direction from the horizontal direction and does not contribute to improving the heat distribution in the horizontal direction, the heat capacity of the reflective layer itself is large, and the cooling rate of the recording layer is rather lowered. Further, the microscopic flatness of the film surface is also deteriorated.

Further, Ag, Ti, V, Ta, Nb,
W, Co, Cr, Si, Ge, Sn, Sc, Hf, P
An Ag alloy containing d, Rh, Au, Pt, Mg, Zr, Mo, or Mn in an amount of 0.2 to 5 atomic% is also desirable. When more importance is placed on the stability over time, Ti and Mg are preferable as the additional components. When the above Ag alloy is used as the reflection layer, the preferable thickness is 40 nm or more and 150 nm or less. If it is less than 40 nm, the heat radiation effect is insufficient even with pure Ag. If it exceeds 150 nm, heat escapes in the vertical direction from the horizontal direction, does not contribute to the improvement of the heat distribution in the horizontal direction, and an unnecessary thick film reduces productivity. Further, the microscopic flatness of the film surface is also deteriorated.

The inventors of the present invention described above,
It has been confirmed that the added element to g increases the volume resistivity in proportion to the concentration of the added element. By the way, it is considered that addition of an impurity generally reduces the crystal grain size, increases electron scattering at the grain boundary, and lowers the thermal conductivity. Adjusting the amount of added impurities is necessary to increase the crystal grain size to obtain the original high thermal conductivity of the material. The reflective layer is usually formed by a sputtering method or a vacuum evaporation method. The total impurity amount including the amount of moisture and oxygen mixed at the time of film formation is 2 atomic% as well as the amount of impurities in the target and the evaporation material itself. It is necessary to: For this reason, it is desirable that the ultimate vacuum of the process chamber is 1 × 10 ⁻³ Pa or less. If a film is formed at an ultimate vacuum degree lower than 10 ⁻⁴ Pa, it is desirable to set the film formation rate to 1 nm / sec or more, preferably 10 nm / sec or more to prevent impurities from being taken in.

Alternatively, when the intentional additive element is contained in an amount of more than 1 atomic%, it is desirable to set the film forming rate to 10 nm / sec or more to prevent the addition of additional impurities as much as possible. The film forming conditions may affect the crystal grain size irrespective of the amount of impurities. For example, in an alloy film in which about 2 atomic% of Ta is mixed into Al, an amorphous phase is mixed between crystal grains, but the ratio of the crystalline phase to the amorphous phase depends on film forming conditions. For example, as the sputtering is performed at a lower pressure, the proportion of the crystal part increases, the volume resistivity decreases, and the thermal conductivity increases. The impurity composition or crystallinity in the film also depends on the manufacturing method of the alloy target used for sputtering and the sputtering gas (Ar, Ne, Xe, etc.).
As described above, the volume resistivity in the thin film state is not determined only by the metal material and the composition. To obtain high thermal conductivity,
As described above, it is desirable to reduce the amount of impurities,
On the other hand, since pure metals such as Al and Ag tend to be inferior in corrosion resistance and hillock resistance, the optimum composition is determined in consideration of the balance between the two.

It is also effective to form the reflective layer in multiple layers in order to obtain higher heat conduction and higher reliability. At this time, at least one of the low volume resistivity materials having a thickness of 50% or more of the total reflection layer thickness substantially controls the heat radiation effect,
The other layers are configured to contribute to the improvement of corrosion resistance, adhesion to the protective layer, and hillock resistance. More specifically, Ag, which has the highest thermal conductivity and the lowest volume resistivity among metals, has poor compatibility with the S-containing protective layer, and tends to deteriorate slightly when repeatedly overwritten. Further, there is a tendency that corrosion occurs easily in an accelerated test environment of high temperature and high humidity. Therefore, it is also effective to use Ag and an Ag alloy as the low volume resistivity material and provide an alloy layer containing Al as a main component as an interface layer between 1 nm and 100 nm between the upper protective layer and the upper protective layer. When the thickness is 5 nm or more, the layer is easily formed uniformly without forming an island structure. As the Al alloy, for example, Ta, Ti, Co, Cr, Si, Sc, H
f, Pd, Pt, Mg, Zr, Mo, or Mn is 0.2
An Al alloy containing at least 2 atomic% and not more than atomic% is given. If the thickness of the interface layer is less than 1 nm, the protective effect is insufficient, and
If it exceeds 0 nm, the heat radiation effect is sacrificed. The use of the interface layer is particularly effective when the reflective layer is made of Ag or an Ag alloy. This is because Ag is relatively susceptible to corrosion due to sulfurization by contact with the protective layer containing sulfide, which is preferred in the present invention.

Further, when an Ag alloy reflective layer and an Al alloy interface layer are used, Ag and Al are a combination which is relatively easily diffused, so that the Al surface is thicker than 1 nm, and it is more preferable to provide an interface oxide layer by oxidizing the Al surface. preferable. If the thickness of the interfacial oxide layer exceeds 5 nm, particularly 10 nm, it becomes a thermal resistance, which impairs the original purpose, ie, the function of the reflection layer having extremely high heat dissipation, which is not preferable. The multilayer structure of the reflective layer is also effective for obtaining a desired sheet resistivity with a desired film thickness by combining a high volume resistivity material and a low volume resistivity material. Adjusting the volume resistivity by alloying can simplify the sputtering process by using an alloy target, but also causes an increase in the target manufacturing cost and, consequently, the raw material ratio of the medium. Therefore, it is also effective to obtain a desired volume resistivity by multilayering a thin film of pure Al or pure Ag and a thin film of the additive element itself. If the number of layers is up to about three, although the initial apparatus cost increases, the cost of each medium may be reduced. The reflective layer is a multilayer reflective layer composed of a plurality of metal films, the total film thickness is 40 nm or more and 300 nm or less, and 50% or more of the thickness of the multilayer reflective layer has a volume resistivity of 20 nΩ · m or more and 150 nΩ · m or less. (It may be a multilayer). By the way, the thickness of the recording layer and the protective layer is not limited in terms of the above-mentioned thermal characteristics, mechanical strength, and reliability, and the laser beam absorption efficiency is good in consideration of the interference effect associated with the multilayer structure. The amplitude of the signal, that is, the contrast between the recorded state and the unrecorded state is selected so as to increase.

For example, if the medium of the present invention is applied to a rewritable DVD to ensure compatibility with a read-only DVD, the degree of modulation must be high. In addition, a DPD (Differential P
It is necessary that the tracking servo method called hase detection) method can be applied as it is. FIG. 6 shows the DFM when the EFM plus modulated random signal is recorded and reproduced.
3 shows a waveform of a C reproduction signal (reproduction signal including a DC component).
The degree of modulation is defined as the ratio I ₁₄ / I _top between the signal intensity I _{top at} the top of the 14T mark and the signal amplitude I ₁₄ . I
_{The top} actually corresponds to the reflectance in the groove of the unrecorded portion (crystal state). I ₁₄ has a problem of intensity difference and phase difference of reflected light from the crystal part and the amorphous part of the phase change medium. The difference in the intensity of the reflected light is basically determined by the difference in reflectance between the crystalline state and the amorphous state. If the modulation degree after the recording is approximately 0.5 or more, low jitter can be realized, and the tracking servo by the DPD method operates well.

FIG. 7 shows the reflectance in a typical four-layer structure.
A calculation example of the difference is shown. On a polycarbonate substrate, (Z
nS)₈₀(SiO_Two)₂₀Protective layer, Ge_0.05Sb_0.69Te
_0.26Recording layer, (ZnS)₈₀(SiO_Two)₂₀Protective layer, Al
_0.995Ta_0.005A reflective layer was provided. Crack of each layer
As the folding ratio, an actually measured value is used. Each at a wavelength of 650 nm
The complex refractive index of the material is such that the upper and lower protective layers are 2.12-0.0.
i, reflective layer 1.7-5.3i, substrate 1.56, recording
The layer is in an amorphous state (measured immediately after film formation).
2.6i, the crystal state after initialization is 2.3-4.1i.
You. The thicknesses of the recording layer, the second protective layer and the reflective layer are respectively
And constant at 18 nm, 20 nm and 200 nm. No.
1 Normally, the change in amplitude is small as far as
Now, the denominator I _top, That is, the reflectance in the crystalline state
Strongly dependent. Therefore, the crystal state reflectance is as low as possible.
Lower is desirable.

In the calculation example of FIG. 7, the first protective layer was a (ZnS) ₈₀ (SiO ₂ ) ₂₀ film having a refractive index n = 2.12.
In this case, the first minimum value d ₁ is a thickness 50 to 70 nm, the second minimum value d ₂ is a film thickness 200 to 220 nm. Thereafter, it changes periodically. The thickness of the first protective layer at which the reflectance in the crystalline state is minimal is substantially determined only by the refractive index of the protective layer if the recording layer has a high reflectance. The minimum point film thickness at another refractive index n can be almost determined by multiplying d ₁ and d ₂ by 2.1 / n. Usually, the dielectric used as the protective layer is n.
= Is about 1.8~2.3, d ₁ is about 60~80nm. If the refractive index n of the first protective layer is smaller than 1.8, the reflectance at the minimum point increases, and the degree of modulation is remarkably reduced to less than 0.5, which is not preferable. Conversely, 2.
If it is 3 or more, the reflectance at the minimum point is too low, and is 20%.
Cannot be achieved, and focusing and tracking servo become difficult.

In the composition range of the recording layer according to the present invention, FIG.
Optical characteristics almost similar to the above are exhibited. From the viewpoint of productivity, it is desirable that the thickness of the first protective layer be 150 nm or less. At present, the deposition rate of the dielectric protection layer by the sputtering method is at most 15 nm / sec.
This is because spending more than a second increases the cost. In addition, the allowable value of the film thickness variation becomes severe, which is not preferable in production. That is, as seen from FIG. 7, the reflectance shifts Δd from the desired film thickness d _0, in the first minimum value d ₁ near fluctuates by the same in the second minimum value d ₂ vicinity.

On the other hand, the uniformity limit of the film thickness distribution in manufacturing is usually ± 2 to 3% with respect to d ₀ . Therefore, d ₀
Is thinner, the variation width Δd of the film thickness becomes smaller, and the variation in the reflectivity within the disk surface or between the disks can be suppressed, which is advantageous. Therefore, in an inexpensive stationary facing type sputtering apparatus that does not have a substrate revolution mechanism, it is desirable to adopt a film thickness near the _first minimum value d1. On the other hand,
Since a thick protective layer has a great effect of suppressing the deformation of the substrate surface at the time of repeated overwriting, if it is important to improve the durability of repeated overwriting, a film thickness near the _second minimum value d2 should be used. desirable. In a medium in which recording or reproduction is performed by irradiating recording / reproducing light through a substrate, the first protective layer must be thickened to some extent to protect the substrate from heat generated during recording. During recording, the recording layer has a thickness of about 100 nanoseconds,
That is all. For this purpose, the film thickness is preferably set to 50 nm or more. If the thickness is less than 50 nm, microscopic deformation is accumulated on the substrate when recording is repeated, and noise and defects are likely to occur. This is particularly important when the substrate is made of a thermoplastic such as polycarbonate.

Next, an optical recording method which is preferably used in combination with the present medium will be described. A preferred first recording method is
When recording the mark-length-modulated information on the recording medium with a plurality of recording mark lengths, the recording medium is irradiated with a recording light having an erasing power Pe capable of crystallizing an amorphous material between the recording marks. Is the time length of nT (T is a reference clock cycle, n is an integer of 2 or more), and the time length nT of the recording mark is

[0098]

Η ₁ T, α ₁ T, β ₁ T, α ₂ T, β ₂ T,
..., α _i T, β _i T, ..., α _m T, β _m T, η
₂ T

(Where m is the number of pulse divisions and m = n−
k and k are integers satisfying 0 ≦ k ≦ 2. Also, Σ _i (α _i
+ Β _i ) + η ₁ + η ₂ = n, η ₁ is a real number satisfying η ₁ ≧ 0, η ₂ is a real number satisfying η ₂ ≧ 0, and 0 ≦ η ₁ + η ₂ ≦ 2.0
And α _i (1 ≦ i ≦ m) is a real number satisfying α _i > 0,
β _i (1 ≦ i ≦ m) is a real number satisfying β _i > 0, and Σα _i <
0.5n. α ₁ = 0.1 to 1.5, β ₁ = 0.3
To 1.0, β _m = 0 to 1.5, and α _i = 0.1 to 0.
8 (2 ≦ i ≦ m). It should be noted that in the case of 3 ≦ i ≦ m, α _i + β _i-1 = 0.5 to 1.5 and is constant regardless of i. ) And α _i T
Within (1 ≦ i ≦ m) of the recording light barrel Pw ≧ Pe becomes recording power Pw to melt the recording layer is irradiated in a time, beta _i T (1 ≦ i ≦ m) of the 0 <P
b ≦ 0.2 Pe (However, in β _m T, 0 <Pb
≦ Pe) with a bias power Pb.

By using this recording method in combination with the above-described medium, the cooling rate at the time of resolidification of the recording layer is accurately controlled, and at least 3 m / s to 8 m / s, and further, 1 m / s depending on the setting of recording conditions. In a wide linear velocity range from s to 15 m / s, high-density mark length modulation recording with a shortest mark length of 0.5 μm or less becomes possible, overwriting 1000 times or more can be achieved, and less than 10% of the reference clock cycle T. Low jitter can be realized. First, in order to realize high-density mark length modulation recording as described above, a wavelength of 350 to 680 is required.
A laser light beam of nm is focused on the recording layer through an objective lens having a numerical aperture NA of 0.55 or more and 0.9 or less to obtain a minute focused light beam spot.

More preferably, the NA is 0.55 or more.
65 or less. When the NA exceeds 0.65, the influence of the aberration due to the inclination of the optical axis becomes large, so that the distance between the objective lens and the recording surface needs to be extremely short. Therefore,
When a focused light beam is incident through a substrate having a thickness of about 0.6 mm, such as a DVD, the upper limit of NA is about 0.65. Then, as shown in FIG.
By modulating the recording light power to the value, the power margin and the linear velocity margin during recording can be increased. In FIG. 8, the start position of the head recording pulse α ₁ T and the end position of the final off pulse β _m T do not necessarily need to match the start position and end position of the original recording signal. 0 ≦ η ₁ + η ₂
Within the range of ≦ 2.0, η ₁ T may be placed at the beginning and η ₂ T may be placed at the end. Fine adjustment of the length of η ₁ T or η ₂ T in accordance with the lengths of the marks before and after the mark and the length between the marks is also effective for accurately forming the marks.

Alternatively, a good mark may be formed by changing only β _m according to the mark length nT. The last β _m may be set to 0. For example, EFM
The longer the mark, the longer the mark, such as the 11T mark out of the 3T to 11T mark in the modulation, or the 14T mark out of the 3T to 14T mark in the EFM plus modulation, so that the last β _m is lengthened and the cooling time is increased. It is better to make it longer. Conversely, in the case of a short mark such as a 3T mark, it is preferable to shorten β _m . The adjustment width is about 0.5. In the case of high-density recording exceeding the linear recording density of a so-called DVD, a sufficient recording signal quality can be obtained without such fine adjustment.

The mark shape can also be controlled by changing the magnitude of the bias power Pb. FIG. 9 shows an example of a temporal change in the temperature of a certain point on the recording layer when two recording pulses are irradiated. While moving the beam relative to the medium, the recording pulse P1, the off pulse, and the recording pulse P
This is a temperature change at the position where the recording pulse P1 is irradiated when the irradiation of No. 2 is continuously performed. (A) is the case where Pb = Pe, and (b) is the case where Pb ≒ 0. FIG. 9B
In this case, since the bias power Pb in the off-pulse section is almost 0, TL 'drops to a point sufficiently lower than the melting point, and the cooling rate on the way is high. Therefore, the amorphous mark is melted during the irradiation of the recording pulse P1, and is formed by rapid cooling during the subsequent off-pulse. On the other hand, in FIG. 9A, the erase power Pe is applied even in the off-pulse section,
The cooling rate after the irradiation of the first recording pulse P1 is slow, and the lowest temperature TL reached by the temperature drop in the off-pulse section is the melting point T.
m, and further heated to near the melting point Tm by the subsequent recording pulse P2, so that an amorphous mark is not easily formed.

It is important for the medium of the present invention to have a steep temperature profile as shown in FIG. 9B in order to suppress crystallization in a high temperature range and obtain a good amorphous mark. That is what. This is because the recording layer of the medium of the present invention shows a high crystallization rate only in the high temperature range just below the melting point, so that the profile of (b) where the recording layer temperature hardly stays in the high temperature range prevents recrystallization. This is because it is considered possible. Alternatively, the generation of crystal nuclei in a relatively low temperature range close to the crystallization temperature Tc is not dominant in each erasing process, and Sb clusters which can be crystal nuclei formed during the above-described initialization exist stably. It is considered that only the crystal growth in the region is dominant. Therefore, by controlling the cooling rate and TL ′, recrystallization is almost completely suppressed, and an amorphous mark having a clear contour substantially coinciding with the molten region can be obtained, and the jitter at the mark edge can be reduced.

On the other hand, in the case of the GeTe—Sb ₂ Te ₃ pseudo-binary alloy, there is no significant difference in the process of forming an amorphous mark in any of the temperature profiles shown in FIGS. 9A and 9B. This is because this material shows recrystallization although its speed is slightly slow even in a wide temperature range, particularly in a low temperature range near the crystallization temperature Tc. Alternatively, in this material, since crystal nucleation in a temperature range relatively close to Tc and crystal growth in a temperature range close to Tm are rate-determining, recrystallization at a relatively low speed over a wide temperature range as a whole. Is thought to occur. GeT
Even in the case of e-Sb ₂ Te ₃ , coarse grains may be suppressed by using an off-pulse with Pb <Pe, but Pb / P
When e ≦ 0.2, crystallization near Tc is excessively suppressed, and the erasing performance is rather deteriorated. However, in the recording layer material according to the present invention, crystallization at a relatively low temperature close to Tc is considered to hardly progress, so that Pb / P
Preferably, e ≦ 0.2. Alternatively, more specifically, it is preferable to use Pb as low as Pb = 1.5 (mW) as long as the tracking servo is stable and to actively use the off-pulse so as to cool as quickly as possible. Is preferable because the edge can be clearly formed.

In the pulse division method shown in FIG.
Tip recording pulse α₁Only T is a subsequent pulse α_iLonger than T
And the leading and trailing off pulse width β
₁T, β _mSet only T separately from other off-pulses
However, this is the most effective way to balance the characteristics of long marks and short marks.
It is valid. State-of-the-art pulse α₁T has no residual heat effect
Therefore, it takes some time to raise the temperature. Alternatively,
The recording power of the leading pulse is higher than the following pulse
Setting is also effective.

[0107] Switching of the pulse is performed at the clock cycle T.
, The pulse control is simplified. FIG. 10 shows a pulse division method suitable for mark length modulation recording and a simple pulse control circuit. (A) shows a case where m = n-1 and (c) shows a case where m = n-2 as a pulse division method when recording mark length modulation data. (B),
In (c), T is omitted to simplify the drawing. In each case, α _i (2 ≦ i ≦ m) and β _i (2 ≦ i ≦ m−
1) is constant regardless of i, α ₁ ≧ α _i , α _i + β _i-1
= 1.0 (3 ≦ i ≦ m), the trailing end of the recording pulse of α _i (2 ≦ i ≦ m) is synchronized with the clock pulse. It is also effective to make Pb the same as the reproducing light power Pr in order to simplify the circuit. Making only the _first pulse α ₁ T longer than the subsequent pulse is necessary to improve the balance between recording short marks and long marks in a so-called eye pattern. Alternatively, only the first pulse may have higher power than the subsequent pulse. Such a pulse can be achieved by determining three types of gate generation circuits as shown in FIG. 11 and the priorities among them.

FIG. 11 shows a pulse emission by the recording method of the present invention.
It is explanatory drawing of an example of a production method. (A) is a clock signal,
(B) is a data signal, which is 3 in the recording pulse generation circuit.
Signal (c) Ga generated from the kind of gate generation circuit
te1, (d) Gate2, and (e) Gate3.
Prioritize these three types of gate signals
Thus, the pulse division method of the present invention can be achieved. Gate1
Is the recording pulse generation interval α₁Only T, Gate2 follows
Pulse α_iTie for generating a predetermined number of T (2 ≦ i ≦ m)
Decide the mining. Where the pulse width α _iIs 2 ≦ i ≦ m
And a constant value α_cAnd Gate 3 is an off-pulse generation section
Interval β _iGenerate T. Gate3 is on (level high)
Pb is generated during the period, and Pe is generated during the off state (low level)
I do. α₁Only the rising timing and pulse width of
By independent decision, β₁To β_iBe different from
Can be. Gate3 and Gate1 rise at the same time
It is good to expect. Gate1 and Gate2 are each
Pw is generated, but when Gate 1 and Gate 2 are on, G
ate3. Gate1 delay time T₁When
α₁, Gate 2 delay time (T ₁+ T_Two) And α_cThe finger
Then, the strategy shown in FIG. 10 can be specified.

Here, if T ₁ is 1T or more, FIG.
The pulse in the case of m = n−1 in FIG. 10B is obtained. If the number of subsequent pulses is reduced by one as less than 1T, m in FIG.
= N-2. At this time, by making α ₁ T and β _m−2 T longer than when m = n−1, the mark length to be formed is set to nT. As a further application example of the present invention, it is desirable to use the following recording method in order to obtain a signal density equal to or higher than that of a read-only DVD at a recording density equal to or higher than that of a read-only DVD.

That is, an optical recording method for recording and reproducing data by condensing light having a wavelength of 350 to 680 nm on a recording layer through an objective lens having a numerical aperture NA of 0.55 to 0.9. = N-1 or m = n-2, 0≤Pb≤
1.5 (mW), Pe / Pw is 0.3 or more and 0.6 or less. Α ₁ = 0.3 to 1.5, α ₁ ≧ α _i = 0.2 to 0.8 (2 ≦ i ≦ m), α _i + β _i−1 = 1.0 (3 ≦ i ≦ m ), Β _m = 0 to 1.5.

The reason why the ratio Pe / Pw is kept constant is to increase the erasing power when the power is high and the recording mark is large when the power fluctuation occurs, thereby expanding the erasable range. If Pe / Pw is less than 0.3, Pe
And the erasure is likely to be insufficient. Conversely, if it is larger than 0.6, the excess of Pe tends to cause re-amorphization at the center of the beam, making it difficult to erase by complete recrystallization. Also,
The amount of energy applied to the recording layer becomes too large, and the recording layer is likely to be deteriorated by repeated overwriting.

Now, the recording layer having the composition according to the present invention has an α
_Since good jitter can be obtained in the range where _i is particularly small,
It is desirable to set α _i <0.5n and to reduce (ｋα _i ) / n as k decreases. That is, k = 0 or k =
In the case of 1, (Σα _i ) <0.4n, and in the case of k = 2, (Σα _i ) <
Preferably, it is 0.5n. Preferably, in order to apply such a recording pulse division method to overwriting at a linear velocity 3m / s or more, the present invention recording layer Ge _x (Sb _y
Te _1−y ) _{1−x In} particular, y is set to 0.72 or more, and y is set to 0.74 or more for overwriting at a linear velocity of 7 m / s or more. That is, the Sb / Te ratio is set to Sb-rich of 2.57 or more, more preferably 2.85 or more.

In the present invention, the composition of the recording layer
High stability of amorphous mark even when rich
Good characteristics is one of the preferable features. Special
Japanese Unexamined Patent Publication No. Hei 8-22644 discloses Sb_0.7Te_0.3Neighborhood
A containing about 10 atomic% of Ag and In in total added to the composition
A gInSbTe recording layer is described. But this
AgInSbTe recording layer with Sb / Te ratio of 2.57 or more
, The amorphous mark becomes extremely unstable and storage stable
There was a problem with sex. Hereinafter, a comparative description will be given using experimental examples.
You. In performing EFM plus modulation mark length recording,
To record a mark of length nT, a linear velocity of 2 m / s to 5 m /
In the range of s, the wavelength is 630-680 nm, NA =
The recording pulse is divided into n-1 using the optical system of 0.6
Consider the case of recording. As an example of the recording layer of the present invention
And Ag_0.05Ge_0.05Sb_0.67Te_0.23(Sb / Te ≒
2.91) and an example of the AgInSbTe recording layer
As Ag_0.05In _0.05Sb_0.63Te_0.27(Sb / T
e ≒ 2.33) is used.

The recording layer of the composition of the present invention is also made of the above AgInSbT
Since the e recording layer also has substantially the same optical constant, the same reflectance and modulation can be obtained using the same layer configuration,
Therefore, a thermally equivalent layer configuration can be applied. 100nm and thickness of the first protective layer, 20 nm of the recording layer, a second protective layer 20 nm, the reflective layer is 200 nm, both beta _i =
About 0.5 (1 ≦ i ≦ n−1), Pw = 10 to 14 (m
W), Pe / Pw = 0.5, Pb ≒ 0. At this time, in the conventional Ag _0.05 In _0.05 Sb _0.63 Te _0.27 recording layer, α ₁ = 0.8 to 1.2 and α _i = 0.4 to 0.6 (2
≤ i ≤ n-1). In particular, α ₁ = 1.0, α
_{When i} (2 ≦ i ≦ n−1) = 0.5 and β _m = 0.5, Σα _i is 0.5n regardless of n.

On the other hand, according to the present invention, Ag _0.05 Ge _0.05 Sb _0.67
In the Te _0.23 recording layer, α ₁ = 0.3 to 0.5, α _i =
A preferred range is 0.2 to 0.4 (2 ≦ i ≦ n−1). More specifically, α ₁ = 0.6, α _i (2 ≦ i ≦ n−
1) = 0.35. In this case, n = 3
Σα _i ≒ 0.32n, and if n = 4 or more, Σα _i ≒ 0.32n
α _i ≒ 0.33n to 0.34n. This means that in the medium of the present invention, the average irradiation power applied during recording can be reduced, and the substantial recording pulse irradiation time can be reduced to Δα _i <0.4n.

As a result, the following effects can be obtained. (1) Deterioration of recording signal quality due to high power recording can be reduced. The problem with high-power recording is that the light energy applied to the recording layer becomes too large and is confined in the recording layer. For this reason, the cooling rate becomes slow, and recrystallization of the amorphous mark occurs, and deterioration during repeated overwriting becomes remarkable. By providing a low-power off-pulse section, the average input power is suppressed, and heat is released in the plane direction by a reflective layer with a high thermal conductivity. , Adverse effects due to heat accumulation can be suppressed, and a good long mark can be formed. (2) Thermal damage of each layer during repeated overwriting can be reduced, and repeated durability can be improved. By reducing the thermal damage each time, for example, deformation of a plastic substrate that is vulnerable to heat can be suppressed. In addition, the range of the damage can be limited to a narrower range at the center of the laser beam profile. In particular, n = 4 where heat is easily stored.
The longer the mark, the greater the effect of reducing the substantial recording energy irradiation ratio (Σα _i ) / n. Therefore, even at a low linear velocity of 5 m / s or less, which is susceptible to thermal damage, adverse effects on the medium can be reduced.

According to the present invention, the durability of repeated overwriting can be improved as described above, and the number of overwriting can be increased by one digit or more as compared with the conventional case. Further, the recording layer is G
_{e x (Sb y Te 1-} y) 1-x alloy film on the basis of (0.045 ≦ x ≦ 0.075,0.74 ≦ y <0.
8), by making the recording pulse division method variable according to the linear velocity, overwriting can be performed in a wide range of linear velocity including 3 m / s to 8 m / s. That is, in the pulse division method of FIG. 8, k of m = nk is fixed, and either Pb / Pe or α _i is monotonously decreased as the linear velocity at the time of overwriting is lower. Note that changing the clock cycle according to the linear velocity in order to keep the recording linear density constant, or changing Pw and Pe so as to keep them optimal at the respective linear velocities may be performed as necessary. .

The present invention further provides a method of recording a so-called EFM plus modulation signal having a shortest mark length of 0.35 to 0.45 μm at both 1 × and 2 × the standard reproduction linear velocity of a DVD. I do. The standard reproduction linear velocity of the DVD is 3.49 m / s. That is, light having a wavelength of 600 to 680 nm and a numerical aperture NA of 0.55 to
An optical recording method for recording / reproducing data through a 0.65 objective lens, condensing light on a recording layer via a substrate, and setting the shortest mark length in a range of 0.35 to 0.45 μm.
n is an integer of 1 to 14, m = n−1, and Pb is 0 ≦
Constant within the range of Pb ≦ 1.5 (mW) regardless of the linear velocity,
Pe / Pw can be changed in accordance with the linear velocity in the range of 0.4 to 0.6. (I) In the range of the recording linear velocity of 3 to 4 m / s, the reference clock cycle is To, and α ₁ = 0.3 to 0.8, α ₁ ≧ α _i = 0.2 to 0.4 and constant regardless of i (2 ≦ i ≦ m), α ₂ + β ₁ ≧ 1.0, α _i + β _{i-1 = 1.0 (3 ≦} i ≦ m), and β _m = 0.3~1.5, α _i T the recording light of recording power Pw ₁ in a time of (1 ≦ i ≦ m) Irradiate,
(Ii) In the range of the recording linear velocity of 6 to 8 m / s, the reference clock cycle is To / 2, α ′ ₁ = 0.3 to 0.8, α ′ ₁ ≧ α ′ _i = 0.3 to 0 0.5 and constant irrespective of i (2 ≦ i ≦ m), α ′ _i + β ′ _i−1 = 1.0 (3 ≦ i ≦ m), β ′ _m = 0 to 1.0, and α _When it is assumed that the recording light of the recording power Pw ₂ is irradiated within the time of _i T (1 ≦ i ≦ m), α ′ _i > α _i (2 ≦ i ≦ m), and 0.8 ≦
This is an optical recording method in which Pw ₁ / Pw ₂ ≦ 1.2. According to the experiments by the present inventors, particularly good jitter was obtained with this setting as long as the pulse division method shown in FIG. 10 was used.

Here, assuming that α ₂ + β ₁ = 1.0, the independent parameters relating to the pulse width are α ₁ , α _i , β
_m , which is preferable because the recording signal source can be further simplified. It is not necessary to take all integers from 1 to 14 as n, and from 3 to 11 and 14 in EFM plus modulation. (1,7) RLL-NRZI (Ru
n Length Limited-Non Return To Zero Inverted) codes and the like can also be used. In general, in order to keep the recording density constant, the clock cycle at the time of 1 × speed recording is set to be twice that at the time of 2 × speed recording. According to the present invention, not only the above-described method (constant linear velocity, CLV method) for recording over the entire recording area while maintaining a constant linear velocity, but also recording over the entire recording area at a constant rotational angular velocity. It is also effective for the method (constant angular velocity, CAV method). Alternatively, it is also effective for a ZCLV (Zoned CLV) system in which the radial direction is divided into a plurality of zones and overwriting is performed in the same zone by the CLV system. The diameter of the optical disk is 86m
m, 90mm (single CD size), 120mm (C
D size) or 130 mm, and the recording area ranges from a radius of 20 to 25 mm to a maximum of about 65 mm. At this time, the difference between the linear velocities of the inner and outer circumferences is nearly three times at the maximum.

In general, in high-density mark length recording, the linear velocity range in which the phase-change medium exhibits good overwrite characteristics is about 1.5 times the linear velocity ratio. When the linear velocity is high, the cooling rate of the recording layer is high, so that an amorphous mark is easily formed. On the other hand, when the linear velocity is reduced, erasure is easy, but the cooling rate of the recording layer is reduced, so that the recording layer is easily recrystallized and a good amorphous mark is not easily formed. In order to solve this problem, it is possible to adjust the thickness of the reflective layer on the inner and outer circumferences so that the degree of heat dissipation by the reflective layer on the inner circumference is increased. Or,
It has also been proposed to change the composition of the recording layer to increase the crystallization rate at the outer periphery or to lower the critical cooling rate required for amorphous formation at the inner periphery. However, it is not easy to create a disk having such a distribution.

On the other hand, according to the combination of the medium and the optical recording method of the present invention, if the linear velocity at the outermost circumference of the disk, that is, the maximum linear velocity is approximately 10 m / s or less, the CAV method or the ZCLV
Also in the system, good recording is possible. The present invention
As described above, in order to use the medium in which the linear velocity changes depending on the radius, it is necessary to divide the recording area into a plurality of zones according to the radius, and switch and use the data reference clock frequency and the pulse dividing method for each zone. desirable.

That is, an optical device having a predetermined recording area
By rotating the information recording medium at a constant angular velocity,
A method of recording based on the mark length.
Linear velocity at 2 to 4 m / s at the outermost circumference of the recording area
Rotating the medium so that the speed is 6 to 10 m / s,
The recording area consists of a plurality of zones separated by a radius.
The recording density is almost the same according to the average linear velocity in each zone.
The reference clock period T is changed so as to be constant. this
When the pulse division number m is constant regardless of the zone,
From the zone toward the inner peripheral zone, the Pb / Pe ratio and / or
Or α_i(I is at least one of 1 ≦ i ≦ m) monotonically
Decrease. As a result, the inner circumference at low linear velocity
The formation of amorphous marks was incomplete due to insufficient cooling rate.
Can be prevented. Note that α _i(I is 1 ≦ i ≦
at least one of m) monotonically decreases
If α₁, Α_Two, ..., α_mΑ in_TwoOnly decrease
Refers to More specifically, the pallet shown in FIG.
Pulse division method based on linear velocity based on
Use simplifies the variable pulse division method circuit.
It is desirable to be able to. At that time, the recording area is
divided into p zones, and the clock period for each zone
And change the pulse division method according to the radial position
It is simpler than changing continuously.

In the present invention, the recording area is divided into p zones by radius, the innermost side is the first zone, the outermost side is the pth zone, and the qth zone (where q is 1 ≦ q ≦
ω _q , and the average linear velocity is <v _q
> _Ave , maximum linear velocity < _vq > _max , minimum linear velocity <v
_{q> min,} the reference clock period T _q, if the time length of the shortest mark and _{n min T q, <v p} > ave / <v 1>
_ave is in the range of 1.2 to 3, and <v _q > _max / <v
_q > _min is preferably 1.5 or less. In the same zone, the same clock period and the same pulse division method are used, but the linear velocity range that can be covered by the same pulse division method is generally limited to 1.5 times.

In the same zone, ω _q , T _q ,
α _i , β _i , Pe, Pb, and Pw are constant, and the physical length n _min T _q <v _q > _ave of the shortest mark is 0.5 μm.
m, T _q <v _q > _ave is substantially constant for all q _satisfying 1 ≦ q ≦ p, and m = n−1 or m = n−2, α ₁ = 0.3 ~ 1.5, α ₁ ≧ α _i = 0.2-0.8 (2 ≦ i ≦ m), α _i + β _i-1 = 1.0 (3 ≦ i ≦ m), 0 ≦ Pb ≦ 1. 5 (mW), and 0.4 ≦ Pe / Pw ≦ 0.6. Here, when m = n-1, α ₁ = 0.3 to
1.5, α _i = 0.2 to 0.5, α when m = n−2
It is preferable that ₁ = 0.5 to 1.5 and α _i = 0.4 to 0.8.

It is important that the pulse division method is changed according to the following rules. Pb, P for each zone
w, Pe / Pw ratio, α _i , β ₁ , β _m are variable, and at least α from the outer zone toward the inner zone.
_i (i is at least one of 2 ≦ i ≦ m) is monotonously reduced. The change of α _i for each zone is preferably in increments of 0.1T or in increments of 0.01T. Here, 1/10 of the reference clock cycle T _p in the outermost peripheral zone
By adding a high-frequency base clock generation circuit having a cycle of about 0, it is possible to generate _Tq and the divided pulse length in all zones as multiples of the base clock. In a DVD, the reference clock frequency at 1 × speed is about 26 MHz, so a base clock frequency of about 2.6 GHz at maximum, usually 260 MHz at least one digit lower.
A base clock frequency of about z is sufficient.

Further, the maximum value of Pw in the recording area
To Pw_max, The minimum value is Pw_minWhere Pw_max/
Pw_min≦ 1.2, Pe = Pw = 0.4-0.6,
0 ≦ Pb ≦ 1.5 (mW). to this
According to this, the setting range of the three types of power can be limited,
The power generation circuit can be simplified. In the present invention, further,
Pulse division method with Pw, Pe / Pw ratio and Pb constant
Support all linear velocities by changing only the law
Is also possible. Also, β _mIs constant regardless of the zone,
α₁And α_mOnly zone-dependent parameters
Wear. This simplifies the drive's recording pulse control circuit
It is extremely useful in performing

In the present invention, when recording, the optical head
Virtually set zones on recording media from radial position information
May be recorded on the disc or written on the disc in advance.
According to the address information and zone information
A zone structure may be physically provided on the network. Virtual
Line speed, whether physical or physical
May be selected according to the recording pulse division method. next,
Another example in which the optical recording method of the present invention is applied to the ZCAV system
Is described. Recording area has p zones depending on radius
The innermost side is the first zone, and the outermost side is the p-th zone.
And zone q (where q is an integer satisfying 1 ≦ q ≦ p).
The angular velocity at_q, Average linear velocity <v
_q>_ave, Maximum linear velocity <v_q>_max, Minimum linear velocity <
v_q>_min, The reference clock period is T_qAt the shortest mark
Intermediate length is n _minT_qAnd In ZCAV system
Is set so that the recording linear density is almost constant.
As the state shifts to the reference clock T,_qIs small
It is necessary to cut. That is, T_q<V_q>
_aveBecomes almost constant for all q satisfying 1 ≦ q ≦ p
So, T depending on the zone_qTo change. Where
The irregularity includes an error of about ± 1%. Ma
The maximum linear velocity and the minimum linear velocity in the same zone are within a certain range.
In order to

[0128]

(< _Vq > _max− < _vq > _min ) / (< _vq > _max + < _vq > _min ) <10% (2)

The width of the zone is determined so as to satisfy the condition. That is, (<v _q > _max− <v _q > _min ) becomes (<v _q >
_max + < _vq > _min ), and the width of the q-th zone is allowed to be less than ± 10% of the average radius < _rq > _ave . More preferably, (< _vq > _max− < _vq > _min ) is (< _vq > _max
+ < _Vq > _min ). The zone width may be such that the recording area is equally divided for each radius, but may not be equally divided as long as this condition is satisfied. Depending on the recording area width,
The recording area having a width of 30 to 40 mm is divided into about 10 or more.

According to the study of the present inventors, the jitter value was at a practical level even if the shortest mark length was about 0.4 μm, provided that the expression (2) was satisfied. The above two conditions are conditions for keeping the recording linear density constant, and for keeping the physical length of the mark or the channel bit length constant. Note that the channel bit length is a length per channel bit along a track. In order to ensure the playback compatibility with DVD more reliably, the reference playback speed v should be about 3.5 m / s,
When the reference clock cycle T is about 38.2 nsec,
It is preferable that the variation of the channel bit length vT be less than approximately ± 1%. In order to satisfy this condition in the ZCAV medium, the following equation (3) is used.

[0131]

(< _Vq > _max− < _vq > _min ) / (< _vq > _max + < _vq > _min ) <1% (3)

Must be satisfied. That is, (<v
_q > _max− < _vq > _min ) is (< _vq > _max + < _vq >
_min ), and the width of the q-th zone is
Average radius < _rq > It is assumed that a radius position less than ± 1% of _ave is allowed. For this reason, the recording area is divided into 200 or more zones. And,

[0133]

[Number 16] _{T q <v q> ave =} vT (4)

It is assumed that T _q <v _q > _ave is substantially constant for all q _satisfying 1 ≦ q ≦ p. Here, substantially constant includes an error of about ± 1%. This allows pseudo-equal density recording regardless of radius in spite of the ZCAV system, so that reproduction is possible even in the CLV system, and compatibility with the CLV DVD player is enhanced. If necessary, the zone width may be smaller.

Under the above conditions, the DVD
An optical recording method for obtaining a recording density equivalent to that described above will be described.
Light having a wavelength of 600 to 680 nm and a numerical aperture NA of 0.5
When recording and reproducing data by condensing light on a recording layer through a substrate through a 5-0.65 objective lens, the innermost circumference of the recording area is within a radius of 20 to 25 mm, and the outermost circumference is The radius is 55-60 mm, the average linear velocity of the innermost zone is 3-4 m / s, and the angular velocity in the q-th zone (where q is an integer of 1 ≦ q ≦ p) is ω _q ,
The average linear velocity is <v _q > _ave , and the maximum linear velocity is <v
_{Assuming that q} > _max , the minimum linear velocity is <v _q > _min , the reference clock cycle is T _q , and the time length of the shortest mark is n _min T _q , n is an integer of 1 to 14, and m = n− 1 and ω
_q , Pb and Pe / Pw are constant regardless of the zone,
T _q <v _q > _ave is substantially constant for all q _satisfying 1 ≦ q ≦ p, and

[0136]

## EQU17 ## (<v _q > _max− <v _q > _min ) / (<v _q
> _Max + < _vq > _min ) <10%

Met [0137], (i) in the first zone, alpha ¹ ₁ = 0.3 to 0.8, regardless of a _{^{α 1 1 ≧ α 1 i =}} 0.2~0.4 i constant (2 ≦ i ≦ m), α 1 2 + β 1 1 ≧ 1.0, and _{^{α 1 i + β 1 i-}} 1 = 1.0 (3 ≦ i ≦ m), (i
i) In the p-th zone, α ^p ₁ = 0.3 to 0.8,
alpha ^p A ₁ ≧ α ^p _i = _0.3~0.5 constant irrespective of i (2 ≦ i ≦ m) , α p i + β p i-1 = 1.0 (2 ≦ i
≦ m), (iii) in other zones,
α ¹ _i ≦ α ^q _i ≦ α ^p _i (2 ≦ i ≦ m), and α
^q ₁ performs recording as a value between alpha ¹ ₁ and alpha ^p _1.

The innermost circumference of the recording area has a radius of 20 to 25 m.
m and the outermost circumference is in the range of a radius of 55 to 60 mm, the radius width of the recording area is about 30 to 40 mm. Then, place the disc in the innermost first zone <
Rotate at a constant angular velocity so that v ₁ > _ave = 3-4 m / s. For the first zone and the p-th zone, recording is performed under the above conditions, and the other zones (the q-th zone where 2 ≦ q ≦ p−1)
Zone), α ¹ _i ≦ α ^q _i ≦ α ^p _i (2 ≦ i ≦
m) and then, alpha ^q ₁ is a value between the alpha ¹ ₁ and alpha ^p _1.
In this case, it is desirable to set the value of α ^q ₁ in increments of 0.1T or 0.01T. Preferably, α ¹ ₁ ≧ α ^q
₁ ≧ _α ^p _{1 ^{(However, α 1 1> α p 1}} ) and.

Further, Pb, Pe / Pw, β₁, Β_mIs
Constant regardless of the zone, α₁, Α_iOnly to zones
If it changes more, it will cover all linear speeds 3-8m / s.
Obtaining good overwrite characteristics over a wide linear speed range
Can be. Preferably, these Pe / Pw, Pb, P
w, β_m, (Α¹ ₁, Α^p ₁), (Α ¹ _c, Α^p _c) Number
Pre-pit row or groove deformation on the substrate in advance
, For each recording medium, and for each
Optimal pulse division method and power for each zone
Can be selected. These are usually recorded
Recording at a position adjacent to the innermost or outermost end of the area
Is done. Make bias power Pb the same as reproduction power Pr
If so, do not dare describe the bias power Pb.
In some cases, it is not necessary. Groove deformation specifically means groove meandering
(Wobble).

Alternatively, an optical information recording medium in which address information is previously recorded on a substrate by deformation of a pre-pit row or a groove includes information on appropriate α ₁ and α _{i in the} address together with the address information. Is also good. Thereby, the pulse division method information can be read together with the address information at the time of access, and the pulse division method can be switched. The pulse division method suitable for the zone to which the recording medium and the address belong can be performed without special correction. Can be selected.

The above-described method of performing recording over the entire circumference of the disk while changing the recording pulse division method for each zone can be applied to the ZCLV method (Zoned CLV). A specific example will be described below. The recording area is divided into a plurality of zones in the radial direction, within each zone, and performs recording at a constant linear velocity, recording linear velocity in the recording linear velocity v _in the outermost zone in the innermost zone v _{ou t} the ratio of v _out / v _in is 1.2~2, α _i =
0.3 to 0.6 (2 ≦ i ≦ m) and β _m = 0 to 1.5, and m, α _i + β _i−1 (3 ≦ i ≦ m) regardless of the linear velocity,
Recording is performed by keeping α ₁ T, Pe / Pw, and Pb constant and changing α _i (2 ≦ i ≦ m) and / or β _m according to the linear velocity. The ZCLV method is similar to the ZCAV method in that a recording area is divided into a plurality of zones in the radial direction. However, in the same zone, recording is performed while rotating the disk at a constant linear velocity in the CLV mode.

Therefore, when the recording method of the present invention is applied to the ZCLV system, when the linear velocities of the innermost zone and the outermost zone are V _in and V _out , respectively, the difference between V _in and V _out is small. By setting V _out / V _in to 1.2 to 2, for example, the load on the medium that depends on the linear velocity is reduced. The medium of the present invention can record over a wide range of linear velocity of 3 to 8 m / s by only slightly changing the recording pulse division method.
A ZCLV system that divides into a relatively small number of zones can be applied. At this time, in order to like recording density regardless of the zone, the reference clock period T _q of the recording data at a linear velocity V _q and each zone in each zone, T _q <v _q> the _ave q
Approximately constant regardless of

In each zone, the optimized
A recording pulse division method is used. That is, α_i= 0.3
0.5 (2 ≦ i ≦ m) and β_m= 0 to 1.5, line
M, α regardless of speed_i+ Β_i-1(3 ≦ i ≦ m), α
₁T, Pe / Pw, and Pb are fixed, and according to the linear velocity
And α_iAnd / or β_mRecord by changing
U. The CLV method, ZCAV method, or Z
In CLV system, according to the linear velocity at the time of overwriting
The example of making the recording pulse division method variable is mainly β _mTo
Simplify the pulse generation circuit by keeping it constant regardless of the linear velocity
, But conversely, β_mActively change
It is also possible to simplify the pulse generation circuit.
You.

In other words, when recording information with a plurality of recording mark lengths having a minimum mark length of 0.5 μm or less, the crystal part is in an unrecorded / erased state and the amorphous part is in a recorded state.
Between recording marks, an erasing power P that can crystallize an amorphous phase
When the recording light of e is irradiated and the time length of one recording mark is nT (T is a reference clock cycle, n is an integer of 2 or more), the time length nT of the recording mark is

[0145]

[Expression 18] η ₁ T, α ₁ T, β ₁ T, α ₂ T, β ₂ T,
..., α _i T, β _i T, ..., α _m T, β _m T, η
₂ T

(Where m is the number of pulse divisions and m = n−
k and k are integers satisfying 0 ≦ k ≦ 2. Also, Σ _i (α _i
+ Β _i ) + η ₁ + η ₂ = n, η ₁ is a real number satisfying η ₁ ≧ 0, η ₂ is a real number satisfying η ₂ ≧ 0, and 0 ≦ η ₁ + η ₂ ≦ 2.0
And α _i (1 ≦ i ≦ m) is a real number satisfying α _i > 0,
β _i (1 ≦ i ≦ m) is a real number satisfying β _i > 0. α ₁ =
0.1-1.5, β ₁ = 0.5-1.0, β _m = 0
1.5, _i is 2 ≦ i ≦ m, and α _i is 0.1 to
It is in the range of 0.8 and constant regardless of i. Incidentally, 3 ≦ i ≦ m becomes alpha _i + beta _i-1 in i is 0.5
It is in the range of 1.5 and constant regardless of i. )
And irradiates a recording light with a recording power Pw of Pw> Pe to melt the recording layer within a time of α _i T (1 ≦ i ≦ m), and β _i T (1 ≦ i ≦ m). ), The recording light having a bias power Pb of 0 <Pb ≦ 0.2Pe (however, in β _m T, 0 <Pb ≦ Pe) is irradiated, and m and α are independent of the linear velocity. _i +
β _i-1 (3 ≦ i ≦ m), α ₁ T, and α _i T (2 ≦ i ≦
This is an optical recording method in which β is made constant so that β _m monotonously increases as the linear velocity decreases.

First, in order to keep the recording density constant, the above-mentioned ZCAV system or ZCLV system is applied, and the reference clock cycle T is changed in inverse proportion to the linear velocity. At least 3 ≦ i ≦ m, preferably the α _i + β _i-1 in the 2 ≦ i ≦ m, by constant irrespective of the linear velocity and i, can simplify the pulse generating circuit, and, alpha _i Can be monotonically decreased as the linear velocity decreases, and the cooling rate of the recording layer can be increased. Normally, α _i + β _i-1 = 1.0. In order to realize such a pulse division method, the width α ₁ T is synchronized with the reference clock cycle T (a certain delay may be added) in the explanatory diagram of the gate generation timing in FIG. One fixed-length pulse (Gat
e1) and a plurality of subsequent fixed-length pulses (Gate 2) having a width α _i T (α _c T) may be generated, and only Gate 3, which determines the final off-pulse length β _m T, may be changed according to the linear velocity.

Here, the maximum recording power at each recording linear velocity
To Pw_max, The minimum recording power is Pw _minThen, Pw_max/ Pw_min≦ 1.2, Pe / Pw = 0.4-0.6, and 0 ≦ Pb ≦ 1.5 (mW). Also, as mentioned above, at least
When the linear velocity during overwriting is 5m / s or less
To prevent thermal damage during repeated overwriting
In addition, when m = n-1, Σα_i<0.4n, m =
In n-2, Σα_i<0.5n is preferred
No.

[0149] In addition, the beta _m at the maximum line speed during overwriting beta ^H _m, the beta _m at the lowest linear velocity beta ^L _m
Β _m at the linear velocity at each overwriting is β
^L _m and β is a value between ^H _m, Pb irrespective of the recording linear velocity,
A recording method in which the Pe / Pw ratio is constant can be applied. In this case, at least Pe / Pw ratio, Pb, Pw,
If the values of α ₁ T, α _i T, and (β ^L _m , β ^H _m ) are recorded in advance on the substrate of the medium by a pre-pit row or groove deformation, the optimum pulse division method is also automatically performed. Selectable and preferred.

Further, when the maximum linear velocity is up to about twice the minimum linear velocity, an optical recording method in which β _m is constant irrespective of the recording linear velocity while maintaining sufficiently practical signal quality. Is also possible. The CLV type read-only DVD drive generates a data clock and a rotation synchronization signal based on a reference clock cycle obtained by reproducing a mark,
There is a method of performing rotation control.

As described above, the medium on which the mark is recorded by the ZCAV method is a read-only DVD drive of the present method, so that the shortest mark length or the channel bit length is substantially constant regardless of the recording radius. It can be reproduced as it is. That is, the PLL is set so that the reference clock cycle T _q ′ of the data generated from the recorded mark substantially matches the reference data clock Tr of the drive.
Since the rotation synchronization control can be performed by the (Phase Lock Loop) method, even if there is a slight fluctuation of the linear velocity or a fluctuation of the channel bit length, the reproduction circuit can decode the fluctuation as it is.

In particular, in all zones, the shortest mark length is 0.
The EFM plus modulation data recorded so as to be substantially constant at 4 μm achieves CLV rotation synchronization by PLL control from a rotation synchronization signal generated from a recorded mark. At the same time, a reference data clock Tr having a frequency in the range of 25 to 27 MHz is generated. Based on this clock, the data can be reproduced as a CLV recording medium without being aware of transition between zones. Of course, if rotation synchronization is achieved so that the reference data clock becomes Tr / 2, reproduction at double speed becomes possible. Such a P
As a circuit for generating a rotation synchronizing signal by the LL method, a known method for a DVD player or a DVD-ROM drive can be used as it is.

The medium of the present invention can ensure reproduction compatibility with DVDs in all signal characteristics other than the reflectance. For this purpose, recording in the groove is desirable, and it is preferable that the push-pull signal of the groove is small. This is because if the push-pull signal of the groove is large, the tracking servo signal in the DPD method used at the time of reproduction becomes small. Therefore, the groove depth is set to λ / (8
n) It needs to be shallower. Here, λ is the wavelength of the reproduction light in air, and n is the refractive index of the substrate. However, at the time of recording, a push-pull signal is usually used for the tracking servo.

As for the reproduction signal characteristics,
In order to obtain the ratio, the modulation degree Mod is preferably 0.5 or more. Here, Mod is (the amplitude of the envelope of the DC reproduction signal) / (the upper end value of the envelope of the DC reproduction signal). The preferred groove depth is d = λ / (20n) to λ
/ (10n). If it is too shallow than λ / (20n),
The tracking servo is not applied because the push-pull signal at the time of recording becomes too small, and the tracking servo at the time of reproduction is not stable if it is deeper than λ / (10n). For example, when the recording / reproducing wavelength is about 630 to 670 nm and the numerical aperture NA of the objective lens is 0.6 to 0.65, the groove depth is 25 to 40 n.
m is desirable.

Further, in order to secure the same capacity as that of a DVD, the pitch of the grooves is set to 0.6 to 0.8 μm. When the groove pitch is set to 0.74 μm, compatibility with DVD is easily obtained. The groove width is desirably 0.25 to 0.5 μm. If it is smaller than 0.25 μm, the push-pull signal becomes too small. When the width is larger than 0.5 μm, the width between the grooves becomes narrower, so that the resin hardly enters during the injection molding of the substrate,
Accurate transfer to the grooved substrate becomes difficult. In the medium of the present invention, the reflectance decreases after recording. In such a medium, in order to lower the reflectance in the groove,
In order to satisfy RGa <RLa, where RGa is the average reflectance in the groove after recording and RLa is the average reflectance between the grooves after recording, it is desirable that the groove width is smaller than the groove width.

For example, if the groove pitch is set to 0.74 μm for compatibility with DVD, it is preferable that the groove width is narrower than 0.37 μm, which is half the groove pitch. On the other hand, when the average reflectivity in the groove before recording is RGb and the average reflectivity between the grooves before recording is RLb, if RGb> RLb is satisfied as long as RGa <RLa is satisfied, the groove is Set the width to 0.
By setting the thickness to 4 to 0.5 μm, the width of the amorphous mark recorded in the groove may be increased, the modulation degree may be increased, and the jitter may be reduced. Now, these grooves may be periodically deformed in order to access a specific unrecorded track and to obtain a synchronization signal for rotating the substrate at a constant linear velocity. Generally, a wobble meandering in a track crossing direction is often formed. That is, if the groove meanders at a constant frequency f _wo ,
By detecting the frequency, a signal for rotation synchronization can be extracted by the PLL method. The amplitude of the groove meandering is 40 to 80
nm (peak-to-peak value). If it is less than 40 nm, the amplitude is too small to deteriorate the SN ratio. If it exceeds 80 nm, the upper and lower ends of the envelope of the recording signal shown in FIG. 6 contain many low frequency components derived from the wobble signal, and the distortion of the reproduced signal is large. turn into.
When the frequency of the wobble is close to the band of the recording data, the amplitude is desirably 80 nm or less.

[0157] Further, as a carrier wave a meandering frequency f _wo, according to the specific address information, by forming a frequency-modulated or phase-modulated meandering can obtain the address information by reproducing it. By forming the grooves meander meandering frequency f _wo is constant, the reference period T _w or multiple or submultiple thereof wobbling groove signals generated from the f _wo, it is also possible to generate a reference clock signal T for data.
Normally, the wobble cycle is set to a frequency sufficiently lower or higher than the frequency component of the data to prevent mixing with the data signal component and to be easily separated by a band-pass filter or the like. In particular, setting f _wo to be one or two digits lower than the reference clock cycle of data has been put to practical use in recordable CDs and the like. In the medium used for the CLV method, PL
After the L rotation synchronization is achieved, f _wo is multiplied by about one or two digits to generate a data reference clock. Generally, the data reference clock generated by such a method is accompanied by a fluctuation of the same order as the data reference clock (frequency) due to the influence of the rotation synchronization fluctuation (about 0.1 to 1% of f _wo ). Cheap. This degrades the window margin for data detection.

Therefore, in addition to the groove meandering signal, it is also effective to insert a prepit or a special wobble having a large amplitude for every constant data length in order to correct the fluctuation of the data reference clock. On the other hand, if f _wo is the data reference clock frequency (1 / T) or within a range of 1/100 to 100 times that of the data reference clock, the data reference clock is generated as it is based on the extracted wobble signal after the rotation synchronization is achieved. Even so, sufficient accuracy can be secured. That is,

[0159]

[Equation 19] 100 / T ≧ f _wo ≧ 1 / (100T) (5)

It is assumed that In the previously described ZCAV method, the reference clock period T _q is preferably allowed to occur as a multiple or submultiple of the reference period Tw _q of the groove wobbling of each zone. That is, by forming the groove meandering at a constant angular velocity while changing the frequency f _wo for each zone, f
_The reference clock generated as _wo or its multiple frequency can be generated as the data reference clock _Tq . At this time, if the wobble of the groove is set to a relatively high frequency satisfying the expression (5), it becomes easy to generate a data reference clock for each zone. Then, the reference clock _Tq is changed for each zone, and the variable pulse division method can be generated in synchronization with this signal, and the position accuracy and fluctuation of each divided pulse can be reduced, which is preferable. As an example of ZCAV type zone division, it is conceivable that one circumference of a groove is one zone. At this time groove has a wobble period is constant regardless of the zone, the groove pitch TP, the meander period as Tw _0, approximately

[0161]

[Equation 20] 2π · TP = a · Tw ₀ · v ₀ (where a is a natural number)

When the following relationship is satisfied, the period Tw
A wobble having a constant _{value of 0} is formed over the entire recording area, and a number of wobbles increase each time the track is turned one circumference. Then, Tw ₀ is an integral multiple of the reference clock period T, that is, Tw ₀
= MT to (m is a natural number) has become, in the case of generating a reference clock from Tw _0, simply because it if an integral fraction can be simplified a reference clock generation circuit desirable. In this case, m does not need to be approximately a natural number, and a deviation of about ± 5% is acceptable.

That is, for TP = 0.74 μm,
v₀= 3.5 m / s, T = 38.23 nsec, n = 1
Then, m ≒ 34.7, and the wobble period is approximately
Tw ₀= 35T, wobbles included in each round
Increases by one. In this case, the CLV method
In spite of the introduction of wobbles,
Interference because rack wobbles are always in phase
(Beat) fluctuation of wobble signal reproduction amplitude is small
There is an advantage that.

The application examples of the present invention have been described above.
The present invention is effective for improving the linear velocity dependency and the recording power dependency in mark length recording of a phase change medium in general, and is not limited to a rewritable DVD. For example, blue laser light having a wavelength of 350 to 500 nm and NA =
The shortest mark length is 0.3μ using an optical system of 0.6 or more
The medium and recording method of the present invention are also effective when performing mark length modulation recording of m or less. The shortest mark length is preferably about 10 nm or more in consideration of the stability of the mark. In this case, it is necessary to pay attention to flatten the temperature distribution in the cross-track direction, and the thickness of the second protective layer is set to 5 to 15 nm.
It is effective to make it extremely thin. Wavelength 350-45
In the case where a laser beam of 0 nm is used, it is more preferably set to 10 nm or less.

Further, the medium of the present invention may be applied to so-called land & groove recording, in which recording is performed using both grooves as tracks. Although it is difficult to satisfy the same recording characteristics with the land and the groove, the track pitch is easily narrowed while the groove width is wide, which is suitable for high-density recording. Both groove width GW and groove width LW are 0.2 to
By setting the thickness to 0.4 μm, stable tracking servo performance can be obtained despite high density. Also, GW / LW
When the ratio is 0.8 or more and 1.2 or less, the signal quality in both the grooves and between the grooves can be kept equal. In order to reduce crosstalk, the groove depth d = λ / (7n) to λ / (5n) or λ / (5n)
It is desirable to set (3.5n) to λ / (2.5n).

[0166]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.
In the following examples, the substrate was made by injection molding. The substrate was an injection-molded polycarbonate resin substrate having a thickness of 0.6 mm, and a groove pitch of 0.74 μm, unless otherwise specified.
A groove having a width of 0.34 μm and a depth of 30 nm formed on a spiral was used. Unless otherwise specified, grooves have a linear velocity of 3.
At 5 m / s, the wobble has a frequency of 140 kHz, and the amplitude of the wobble is about 60 nm (peak-to-p).
eak value).

The groove shape was measured using an optical diffraction method similar to a U groove. The groove shape may be measured with a scanning electron microscope or a scanning probe microscope. In this case, the groove width at a position half the groove depth is used. Unless otherwise specified, after forming a four-layer structure as shown in FIG.
A protective layer made of an ultraviolet curable resin is provided thereon by spin coating, and another protective layer having the same layer structure as 0.6 mm
It was bonded to a thick substrate. In the following examples and comparative examples, the first protective layer in FIG. 5A is referred to as a lower protective layer, and the second protective layer is referred to as an upper protective layer.

The recording layer immediately after the film formation is amorphous, and has a wavelength of 810 to 8 collected at a major axis of about 90 μm and a minor axis of about 1.3 μm.
A linear velocity of 3.0 to 6.0 with a laser beam of 30 nm.
An appropriate linear velocity was selected within the range of 0 m / s, and the whole surface was melted by irradiating light with an initialization power of 500 to 700 mW to recrystallize to obtain an initial (unrecorded) state. The composition of each layer was confirmed by a combination of fluorescent X-ray analysis, atomic absorption analysis, X-ray excited photoelectron spectroscopy, and the like. The film densities of the recording layer and the protective layer were determined from the weight change when the film was formed to a thickness of about several hundred nm on the substrate. The film thickness was used by calibrating the fluorescent X-ray intensity with the film thickness measured by a stylus meter. The area resistivity of the reflective layer is 4 probe resistance meter ｛L
oresta FP, (trade name) manufactured by Mitsubishi Yuka (currently Dia Instruments) Co., Ltd. The resistance was measured with a reflective layer formed on a glass or polycarbonate resin substrate as an insulator, or with a four-layer structure (before the UV-curable resin protective coat) shown in FIG. . Since the upper protective layer is a dielectric thin film and an insulator,
The four-layer configuration does not affect the measurement of the sheet resistivity of the reflective layer. Also, a diameter of 1 which can be regarded as a substantially infinite area
The measurement was performed with a disk substrate shape of 20 mm. Based on the obtained resistance value R, the area resistivity ρs and the volume resistivity ρv were calculated by the following equations.

[0169]

Ρs = F · R (6) ρv = ρs · t (7)

Here, t is the film thickness, and F is a correction coefficient determined by the shape of the thin film region to be measured, and takes a value of 4.3 to 4.5. Here, it is set to 4.4. Unless otherwise specified, a DDU1000 evaluator manufactured by Pulstec was used for recording / reproduction evaluation. The wavelength of the optical head is 637 nm, and the numerical aperture NA of the objective lens is 0.6 or 0.63. The beam diameters are about 0.90 μm and about 0.87 μm, respectively. Note that the beam diameter corresponds to a region where the energy intensity of a Gaussian beam is 1 / e ² or more of the peak intensity.

The recording is performed by the pulse division method shown in FIG.
Unless otherwise specified, m = n-1 and α _i + β _i-1 = 1.
0 (2 ≦ i ≦ m). Pb was constant at 1.0 mW which is the same as the reproducing power at all linear velocities. Pe / P
w was constant at 0.5 unless otherwise specified. Pb,
The modulation degree and the jitter were measured by changing Pw while keeping constant between 0.8 and 1.0 mW. The signal to be recorded is DVD
The random mark used was 8-16 modulation (EFM plus modulation), and the minimum mark length was 0.4 μm unless otherwise specified. Unless otherwise specified, the measurement was performed with only a single track recorded.
There is no influence of crosstalk. Recording was performed at various linear speeds such as 1 × speed and 2 × speed, with the standard linear speed of 3.5 m / s of DVD being 1 × speed.

The reproduction was always performed at a linear velocity of 3.5 m / s, and the jitter was measured after binarizing the reproduced signal after passing through the equalizer. Note that the jitter refers to edge-to clock jitter, and the measured value is expressed as% of the reference clock cycle T. The characteristics of the equalizer conformed to the read-only DVD standard. Reference clock cycle T =
38.2 nsec. (26.16 MHz) and less than about 10% (preferably less than 8%) jitter and 5%.
It is preferable to obtain a modulation degree of 0% or more, preferably 60% or more. Furthermore, the jitter increase after repeated overwriting is small, and after at least 100 times,
Preferably, even after 1000 times, it is desirable to be able to maintain less than 13% of T. From the standpoint of ensuring compatibility with a read-only DVD, it is important to measure the reproduction light at 650 to 660 nm, but in the present invention, the wavelength only slightly affects the shape of the focused light beam. By adjusting the reproduction optical system, 637n as used in the present invention can be used.
It has been confirmed that the same jitter as in the m optical system can be obtained in the 660 nm optical system.

(Example 1 and Comparative Example 1) As the recording layer,
InGeSbTe system according to the present invention and conventionally known InAg
In order to compare the SbTe quaternary system, a medium in which recording layer compositions and layer configurations were almost strictly prepared except for the composition of Ag and Ge was prepared as shown in Table 1. Except for replacing Ag and Ge in both recording layers, the composition is within a range that can be regarded as sufficiently equivalent within a range of the measurement error. The reason why the thicknesses of the lower protective layers are different is that the reflectance Rtop of the medium is adjusted to be the same. Such correction is necessary because the refractive index of the recording layer is slightly different.However, in order to make the same light absorption efficiency to the recording layer and the same thermal damage effect due to the reproduction light, a comparison was made. Is the necessary correction.
Since the thickness of the recording layer and the thickness of the upper protective layer are the same, the heat radiation effect and the thermal damage can be regarded as equivalent. The substrate is made of a polycarbonate resin having a thickness of 0.6 mm and a groove pitch of 0.1 mm.
A groove having a width of 74 μm, a groove width of 0.34 μm, a groove depth of 27 nm, a wobble frequency of 140 kHz (linear velocity of 3.5 m / s), and a wobble amplitude of 60 nm (peak-to-peak value) is formed and recorded in the groove. Was done.

[0174]

[Table 1]

When recording was performed by EFM plus modulation on these two types of media at a recording linear velocity of 3.5 m / s and T = 38.2 nanoseconds, good overwrite recording characteristics were exhibited. The overwrite recording conditions were not the conditions under which the characteristics of the respective discs were always the best, but were performed under the common condition that both characteristics were almost the same as shown in Table 1. That is, in the pulse division method shown in FIG. 10A, m = n−1, α _i + β _i−1
= 1.0 (2 ≦ i ≦ m), α _i = α _c = constant (2 ≦ i ≦
m), α ₁ = 0.5, α _c = 0.3, β _m = 0.5
Pw = 13.5 mW, Pe = 6.5 mW, Pb =
0.8 mW. The signal thus recorded was repeatedly irradiated with reproduction light, and the reproduction light stability was examined. After irradiating a predetermined number of times with a predetermined reproduction light power Pr, the reproduction light power was sufficiently reduced to 0.5 mW to measure jitter and the like. The result is shown in FIG. The medium of the first embodiment has a reproduction light power of 1
It did not show a degradation due to reproducing light at all until mW in 10 ^six times. When the power is increased by 0.1 mW, the deterioration is gradually accelerated.

On the other hand, the medium of Comparative Example 1 had a reproduction light power of 1
For all reproduction light of mW or more, the first 100 to 1
The jitter suddenly increases up to 000 times and then gradually worsens. Although the jitter value is high as a whole, the initial jitter deterioration is fatal. In Comparative Example 1, the degree of modulation was also reduced by the reproduction light, and was reduced by about 10% after about 100 irradiations and calmed down. Initially, the jitter increases sharply,
It is considered that the decrease in the degree of modulation progresses unevenly. The recorded media of Example 1 and Comparative Example 1 were subjected to 80 ° C./80% R
H was left in an environment of H and the accelerated test was performed.
After 0 hour, the characteristics of the disk of Example 1 hardly changed at all, whereas the recording signals of the disk of Comparative Example 1 were almost completely erased. It can be seen that the amorphous mark is extremely unstable in the recording layer material having the composition of Comparative Example 1.

As described above, the disc of Example 1 is excellent not only in initial overwrite recording characteristics but also in reproduction light stability and stability with time. This is Sb _0.7 T
In an alloy system containing excess Sb in e _0.3, a suitable amount of addition of Ge is shown to be very effective. The acceleration test was performed on the medium of Example 1 in an environment of 80 ° C./80% RH. An accelerated test was performed up to 2000 hours.
The deterioration of the jitter of the signal recorded before the acceleration test was only about 1%. The degree of modulation was 64% at the beginning, but hardly changed to 61% even after the acceleration test for 2000 hours. The reflectance was almost unchanged at all. The deterioration of jitter when new recording was performed on an unrecorded portion after 2000 hours was about 3%, but this is a level that does not hinder practical use at all. Further, in the medium of the first embodiment, the dependency of the jitter on the recording pulse division method is expressed as m = n−1.
And the case where m = n−2 was studied in detail.

FIG. 13 shows that at a linear velocity of 3.5 m / s.
When (a) m = n-1 and (b) m = n-2,
Of jitter when₁, Α_cFIG. 5 is a contour diagram showing dependency.
You. FIG. 14 shows the results at a linear velocity of 7.0 m / s.
(A) When m = n-1, (b) When m = n-2
The jitter of α₁, Α_cFIG. 3 is a contour diagram showing dependency.
Pw, Pe, Pb and β used for measurement in each figure_mOf each figure
Shown above. At a linear velocity of 3.5 m / s, m = n
−1 and m = n−2, α ₁= 0.7-
0.8, α_c= 0.35 to 0.40, the maximum
Low jitter (about 7% or less)
You. At a linear velocity of 7.0 m / s, m = n-1, m = n
-2, in either case, α ₁= Around 0.5, α_c= 0.
Around 40, the lowest jitter is obtained.
Understand. Α near the minimum jitter₁, Α_cTo
Then, in any case, Σα_i<0.5n
Add In this embodiment, the linear velocity is 3.5 m / s and the linear velocity is 7.0.
In any case of m / s, by setting m = n−2,
Lower jitter value, and when m = n-1.
Α larger than₁With low jitter
I have.

Further, the medium of the above-mentioned Example 1 was changed to NA =
Using a 0.63 evaluator, the linear velocity dependence of jitter was evaluated by changing the recording pulse division method as shown in Table-2.
Note that the reference clock cycle T is inversely proportional to the linear velocity.
The pulse division method is as follows: m = n-1, α _i + β _i-1 = 1.0
(2 ≦ i ≦ m), α _i = α _c = constant (2 ≦ i ≦ m). Pw, Pb, and Pe were constant regardless of the linear velocity.
Here, in the pulse dividing method of Table 2, Σα _i <0.5n is satisfied at all linear velocities. Good overwrite characteristics were obtained from 1 × to 2.5 × the standard linear speed of DVD. This medium exhibits good overwrite characteristics over the entire recording area even in the CAV system by dividing the recording area into 3 to 4 zones and slightly changing the recording pulse strategy for each zone.

[0180]

[Table 2]

Similar results were obtained when recording / reproducing was performed using an evaluator having a wavelength of 660 nm and NA = 0.65.

Example 2 A lower protective layer (Zn) was formed on a substrate.
S) ₈₀ (SiO ₂ ) ₂₀ , recording layer Ge _0.05 Sb _0.73 Te
_0.22, upper protective layer _{(ZnS) 80 (SiO 2)} 20, a reflective layer Al _0.995 Ta _{0.00 5,} provided with variously changing the film thickness of each layer. Table 3 shows the thickness of each layer. All thin films were formed by sputtering without releasing the vacuum. The film formation of the reflective layer was performed at an ultimate vacuum of 2 × 10 ⁻⁴ Pa or less, an Ar pressure of 0.54 Pa, and a film formation rate of 1.3 nm / sec. Its volume resistivity is 5
5 nΩ · m and the sheet resistivity was 0.28 Ω / □. Impurities such as oxygen and nitrogen are less than the detection sensitivity in X-ray excitation photoelectron spectroscopy, and can be considered to be less than about 1 atomic% in total. (ZnS) ₈₀ (SiO ₂ ) _{20 The} protective layer has a film density of 3.
50 g / cm ³ , theoretical bulk density 3.72 g / cm ³
94% of ^three . The recording layer density was 90% of the bulk density. The thermal conductivity of the protective layer estimated from the thermal simulation is 3.5 × 10 ⁻⁴ pJ / (μm · K · n
sec).

In the medium prepared in this manner, the pulse division method shown in FIG. 10A was optimized for each layer configuration of each medium at 1 × speed and 2 × speed, and recording (overwriting) was performed. went. After that, the first 10
And after 1,000 times of overwriting, the jitter was measured.
In the measurement, the wavelength 637 nm and NA =
An optical system of 0.63 was used. Table 3 summarizes the optimum pulse division method, jitter, Rtop, and modulation factor at 1 × speed for each medium.

[0184]

[Table 3]

In each case, at 1 × speed, the shortest mark length was 0.4
The mark length modulation recording of μm was performed, and a large initial modulation degree was obtained. When the thickness of the upper protective layer was 20 nm, both the initial jitter and the jitter after overwriting 1000 times were less than 10%. Upper protective layer thickness is 30
When the value is nm, the initial jitter is good, but the increase in jitter due to repeated overwriting is slightly large, and the jitter is 10 to 12% after 1000 times of overwriting.
When the upper protective layer thickness is 40 nm, the initial jitter is 13
% Or more, and suddenly deteriorated by repeated overwriting to 20% or more. Further, when the recording layer thickness is 30
In Example 2 (h2) having a thickness as large as 10 nm, the initial recording jitter was 13% or more, and the deterioration of the jitter due to repeated overwriting was remarkable. In Example 2 (i2) in which the lower protective layer had a thickness of 45 nm, the repeated overwrite durability was poor. Further, when the thickness of the reflective layer is 250 nm, 200
A better jitter than nm was obtained. That is, in such a high-density mark length recording, it is understood that the “ultra-quenching structure” is preferable.

Next, the dependency of jitter on the recording power Pw of the medium of Example 2 (g1) was evaluated. In the pulse division method, m = n−1 in FIG. 10, Pw = 14 mW,
Recording was performed at 1 × speed and 2 × speed, with Pe / Pw = 0.5 and β _m = 0.5. Then, α ₁ and α _c = α _i (2
.Ltoreq.i.ltoreq.m). At 2 × speed, α ₁ = 0.5, α _c = 0.4, β _m = β _n-1 = 0.
5, Pw = 14 mW, α ₁ = 0.7, α at 1 × speed
_c = 0.3, β _m = β _n-1 = 0.5, and Pw = 14 mW. At this time, at 2 × speed, Σα _i = 0.3n (n =
3), 0.33n (n = 4), 0.34n (n = 5),
0.38n or less (n = 6 to 14). At 1 × speed, Σα _i = 0.33n (n = 3), 0.33n (n =
4), 0.32n (n = 5), less than 0.32n (n = 6
１４14). FIG. 15 shows the result. Dependence of jitter on recording power Pw after initial and 10 overwrites, and reflectance Rto after 10 overwrites
p and the degree of modulation Mod depend on the recording power Pw. (A) shows the case of 2 × speed recording, and (b) shows the case of 1 × speed recording. Note that Rtop corresponds to Itop in FIG. In the drawing, DOW (Direct Overwrite) indicates overwriting. Next, the overwrite durability was evaluated. FIG. 16 shows the result. Overwrite 1000 for jitter, reflectance and modulation
The values up to the end are shown. (A) shows the case of 2 × speed recording, and (b) shows the case of 1 × speed recording. In each case, the jitter is
It increased gradually up to about 10 times, but stabilized after 10 times, and there was almost no deterioration in jitter, modulation, and reflectivity up to 1000 times.

Further, this medium was subjected to the same pulse division method as that of the above-mentioned double speed (linear speed of 7 m / s) except that the linear velocity was 9 m / s and the reference clock cycle was 14.9 nsec.
Overwriting was performed at 4 mW. Erasure ratio is 30d
A sufficient value of B or more was obtained. Also, the jitter was as good as less than 11%. For the medium of Example 2 (g1), Pw = 14 m in a linear velocity range of 3 to 8 m / s.
W, Pb = 1 mW, Pe / Pw = 0.5, β _m = 0.5
In a constant, it is good jitter of changing only the alpha ₁ and alpha _c is obtained. That is, when the linear velocity is 3 to 5 m / s, α ₁ = 0.7, α _c = 0.35, and the linear velocity is 5 to 7 m / s.
, Α ₁ = 0.65, α _c = 0.4, linear velocity 7 to
For 8 m / s, α ₁ = 0.55, α _c = 0.45,
If you change it in at least three stages,
% Of good jitter was obtained. 1m /
If α ₁ and α _c are changed at intervals of s, it is considered that better jitter can be obtained at each linear velocity. Note that P
When w = 11 to 14 mW, Pe / Pw is 0.4 to
The best jitter was obtained at 0.5. Also, Pb is 1.5
When the power exceeds mW, the jitter rapidly deteriorated. Where Pe
When Pb dependence was examined with /Pw=0.5, Pb
Is less than 1.0 mW, almost the best jitter was obtained.
That is, Pb / Pe is preferably less than 0.2.

Next, Example 2 (g1) in which the thickness of the upper protective layer is 20 nm is compared with Example 2 (d2) in which the thickness of the upper protective layer is 40 nm. For both media, the recording mark length dependence was measured at 1 × speed as follows. 3T which is the shortest mark in EFM plus modulation using an optical system with NA = 0.6
The mark length dependency of jitter when the mark length was reduced from 0.5 μm was evaluated. The recording linear velocity was constant at 3.5 m / s, the pulse division method was constant as described above, and the mark length was changed by changing the reference clock cycle. However, when the shortest mark length is 0.46 μm or more, the reproduction speed is 3.5 m / s due to restrictions on the device.
In this case, the CLV control becomes difficult, so the reproduction speed is set to 5 m / s.
And Note that the shortest mark length of 0.4 μm is
It corresponds to the VD standard. FIG. 17 shows the result. (A)
Is the medium of Example 2 (g1), and (b) is the medium of Example 2 (d2).
Medium.

It can be seen that the medium of Example 2 (g1) can be used with a jitter of less than 13% up to the shortest mark length of about 0.38 μm. When an optical system with NA = 0.63 was used, it was possible to reduce the jitter by about 2%. Also, by optimizing the equalizer at the time of reproduction, it was possible to reduce the jitter by about 2%. In addition, NA =
If an optical system of 0.65 is used, it is considered that a sufficiently good jitter can be obtained even at 0.35 μm. Example 2 (d
In the medium 2), jitter having almost no problem was obtained at a mark length of 0.45 μm or more, but the jitter increased sharply at a mark length of less than 0.45 μm, and at a mark length of 0.40 μm, the jitter was 13% or more, and the medium was unusable. It has become possible. Next, in order to evaluate the so-called tilt margin, after the EFM plus modulated random pattern signal is recorded over a plurality of tracks on the medium of Example 2 (g1), the substrate is intentionally moved with respect to the optical axis of the reproduction laser beam. By tilting, the change in jitter during reproduction was measured. The optical system for recording / reproducing is NA = 0.6, and the recording linear velocity is 1 × or 2 ×, both of which are reproduction after overwriting 10 times. FIG. 18 shows the measurement results. The tilt margin was ± 0.7 to 0.8 degrees in the radial direction and ± 0.5 to 0.6 degrees in the circumferential direction, which was a level that would not cause a problem in a normal drive.

<Acceleration Test> An EFM-plus-modulated random pattern was recorded on a part of the track of the medium of Example 2 (g1) using the above-mentioned optimal pulse division method with Pw = 13 mW, and the jitter was measured. . After that, the medium was subjected to an acceleration test under high temperature and high humidity of 80 ° C./80% RH. When the jitter of this track was measured again after 500 hours and 1000 hours of the acceleration test, it was found that the jitter only deteriorated by about 1% after 1000 hours. In addition, acceleration test 10
After 00 hours, a random pattern was recorded on another track under the same conditions as above, and the jitter was measured. As a result, a deterioration of about 2% was observed. In addition, recording was similarly performed at 1 × speed and 2 × speed, and
The modulation was evaluated before and after the acceleration test for 1000 hours under the high temperature and high humidity of 0 ° C./80% RH. At 1 × speed, the initial modulation was 61%, and the modulation after the acceleration test was 58%. At 2 × speed, the initial modulation is 60% and the modulation after the acceleration test is 58%
Met. <Stability against reproduction light> The medium of Example 2 (g1) was irradiated with reproduction light at a power increased to 1.2 mW.
No degradation was observed at about 0 minutes. Next, increase the power to 1.0
When the reproduction light was repeatedly irradiated up to 1,000,000 times at mW, the increase in jitter was less than 2%.

Example 3 The composition of the recording layer was Ge _0.05 Sb
_A medium was prepared with the same layer configuration as in Example 2 except that _0.71 Te _0.24 was used. Table 1 shows the thickness of each layer and the evaluation results.
It is shown in FIG. An optical system with NA = 0.63 was used for the measurement. As in Table 3, α ₁ , α _c ,
The jitter was evaluated by optimizing β _n-1 and setting Pw and Pe so that the jitter was minimized. In each case, mark length modulation recording with a minimum mark length of 0.4 μm was performed at 1 × speed, and a large initial modulation degree was obtained. Example 3
As for (a), as in Example 2 (a1), good characteristics were obtained when the recording linear velocity was 1 × and 2 ×, but 9 m / s.
In Example 2, the jitter was higher by 1 to 2% than in Example 2 (a1). Example 3 in which the thickness of the upper protective layer is 30 nm
In (a) to (f), a jitter of less than 10% is obtained, and
It was less than 13% even after overwriting 0 times. In Examples 3 (g) to (i) in which the thickness of the upper protective layer was as thick as 40 nm, the jitter could only be obtained with a value larger than 13%.

[0192]

[Table 4]

Example 4 The layer structure was such that the lower protective layer (Zn
S) ₈₀ (SiO ₂ ) ₂₀ having a thickness of 215 nm and a recording layer Ge
18 S of _0.05 Sb _0.69 Te _0.26 with an upper protective layer (Zn
S) ₈₀ (SiO ₂ ) ₂₀ of 18 nm, reflective layer Al _0.995 T
a _0.005 was set to 200 nm. The composition of the present recording layer has a linear velocity of 3
Good characteristics can be obtained at a recording speed of up to 5 m / s. However, since the amount of excess Sb is slightly smaller than that of Examples 2 and 3, the stability with time is excellent, and it is preferable to emphasize the storage stability of recorded information and deterioration due to repeated reproduction, that is, reproduction light durability. . The following was evaluated using an optical system with NA = 0.6. The optimal pulse division method was determined as follows. Recording linear velocity 3.5m /
In s, Pw = 13mW, and Pe / Pw = 0.5, α ₁ as constant beta _m = 0.5 in FIG. 10, alpha
_The pulse division method that can obtain the minimum jitter by changing _c was selected. FIG. 19 shows the dependency of jitter on α ₁ and α _c after 10 overwrites as a contour map of jitter. Almost the best jitter was obtained by setting α ₁ = 0.4 to 0.8 and α _c = 0.3 to 0.35. Based on this, α ₁ = 0.6 and α _c = 0.35 was selected. At this time, Σα _i = 0.32n (n = 3), 0.33n
(N = 4), 0.3n (n = 5), less than 0.35n (n
= 6 to 14). Modulation degree is 65%
It was a value comparable to VD. Rtop is 23%
In practice, if it is 15% or more, it can be considered that reproduction can be performed with an existing reproduction-only drive. Therefore, the recording medium of the present invention has a Pw of 12.5 mW and a linear velocity of 3.5.
Record image data at m / s.
When I tried to play on the player, the focus servo,
Tracking servo signal and jitter are normal read-only DV
Characteristics equivalent to D were obtained.

<Durability of repeated overwriting> FIG.
In addition, at Pw = 12.5 mW, jitter, Rtop,
The dependence of the degree of modulation on the number of repeated overwrites is shown. 1
Even after overwriting 000 times or more, it shows sufficiently stable characteristics.

<Acceleration Test> Some of the tracks on this medium
Assuming that Pw = 13 mW, an EFM-plus-modulated random pattern was recorded using the above-described optimal pulse division method, and jitter was measured. After that, the medium was heated to 80 ° C /
An acceleration test was performed under high temperature and high humidity of 80% RH. When the jitter of this track was measured again after 500 hours and 1000 hours of the acceleration test, it was found that the track deteriorated by less than 0.5% after 1000 hours. The modulation degree is initially 65%
And 63% after the accelerated test. After 1000 hours of the acceleration test, a random pattern was recorded on another track under the same conditions as above and the jitter was measured.
%, But there is no practical problem with this level.

<Stability with respect to reproduction light> The medium was irradiated with reproduction light at a power of 1.3 mW, but did not deteriorate at all in about 10 minutes. Next, increase the power to 1.0mW
As described above, the reproduction light was repeatedly irradiated up to 1,000,000 times, and the increase in jitter was less than 1%.

[0197] The recording layer in the layer structure of (Example 5) Example 2 (a1) was Ge _0.05 Sb _0.75 Te _0.20. The evaluation was performed with an optical system having NA = 0.6. α ₁ = 0.4, α _c
= 0.3, β _m = 0.5, Pw = 14 mW, Pe / Pw
= 0.5 gave the best jitter. The initial modulation was also sufficiently large. After 10 times of overwriting, the jitter was barely less than 10%, and after 1000 times, less than 13% was maintained.

<Acceleration test> Some tracks of this medium
Using Pw = 14 mW, the EFM plus modulated random pattern was recorded by using the above-mentioned optimal pulse division method, and the jitter was measured. After that, the medium was heated to 80 ° C /
An acceleration test was performed under high temperature and high humidity of 80% RH. After 500 hours of the acceleration test, the jitter of this track was measured again, and it was only about 2% worse. 500 hours after the acceleration test, a random pattern was recorded on another track under the same conditions as above, and the jitter was measured.
Although the degree of deterioration was observed, there is no practical problem with this degree.

<Stability to reproduction light> The medium was irradiated with reproduction light at a power of 1.0 mW, but did not deteriorate at all in about 10 minutes. Next, increase the power to 1.0mW
As described above, the reproduction light was repeatedly irradiated up to 1,000,000 times, but the increase in jitter was less than 3%, and was kept at less than 13%.

(Embodiment 6) In the layer structure of the embodiment 4,
The recording layer was made of Ag _0.05 Ge _0.05 Sb _0.67 Te _0.23 . N
The evaluation was performed using an optical system of A = 0.6. At a linear velocity of 3.5 m / s, the dependency of the jitter on the pulse division method (α ₁ and α _c ) is Pw = 13 mW, Pe / Pw = 0.5, m = n
Measurement at −1, β _m = 0.5 resulted in a contour diagram shown in FIG. α ₁ = 0.6, α _c =
0.35 was almost optimal. In this case, Σα _i = 0.
32n (n = 3), 0.33n (n = 4), 0.33n
(N = 5) and less than 0.35n (n = 6 to 14).

FIG. 21 (b) shows the first time, 10 times, 1000 times.
FIG. 21 shows the power dependency of the jitter after the overwriting.
(C) shows the power dependence of Rtop and the modulation factor after 10 overwrites. Good jitter was maintained in a wide range of recording power up to after overwriting 1000 times, and Rtop 18% and modulation degree 60% or more could be achieved. FIG. 22 shows changes in jitter, Rtop, and modulation at Pw = 13 mW after 10,000 overwrites. There was no deterioration except for the initial increase in jitter of about 1%. FIG. 2 shows the result of measuring the shortest mark length dependency of jitter in the same manner as in Example 1.
3 is shown. 10% jitter with shortest mark length 0.38μm
It was very good with less than. Note that, for this medium, m
The evaluation was also performed on the pulse division method where n = n−2, and the same characteristics as those in FIG. 21 were obtained when α ₁ = 1.0, α _c = 0.5, and β _m = 0.5. Σα _i at n = 3
= 0.48 N, was Σα _i = 0.46n~0.47n with n = 4 Σα _i = 0.48n, at n ≧ 5.

(Comparative Example 2) In the layer structure of Example 6,
The recording layer was made of Ag _0.05 In _0.05 Sb _0.63 Te _0.27 . At a linear velocity of 3.5 m / s, Pw = 13 mW, Pe / P
When w = 0.5 and β _m = 0.5, the dependency of the jitter on the pulse division method was evaluated, and the contour diagram shown in FIG. 24A was obtained. α ₁ = 1.0 and α _c = 0.5 were optimal. In this case, Σα _i was constant at 0.5n regardless of n. FIGS. 24B and 24C show the recording power dependency and the repetitive overwrite characteristics up to 1000 times. The jitter and power margin in the first recording were better than in Example 5, but deteriorated due to repeated overwriting, and became worse rather after 1000 times. When the reproducing light power was further increased to 1 mW, 5
The jitter deteriorated in about a minute and increased to more than 10%. This difference cannot be explained by a recording sensitivity difference of 0.5 to 1 mW. The main cause of the reproduction light deterioration is that the temperature rises to about 50 to 100 ° C., and it can be seen that the Ge addition of the present invention is effective for improving the thermal stability of the amorphous mark.

(Comparative Example 3) The layer structure was changed to (ZnS) ₈₀ (S
iO ₂ ) ₂₀ Lower protective layer having a thickness of 90 nm, Ge ₂ Sb ₂ T
e ₅ recording layer 21 nm, (ZnS) ₈₀ (SiO ₂ ) ₂₀ upper protective layer 23 nm, Al _0.995 Ta _0.005 reflective layer 2
00 nm. At the time of recording, the pulse division method shown in FIG. 10A was used as a basis, and fine adjustment was performed so that the best jitter could be obtained at each mark length and linear velocity. For this medium, as shown in FIG. 25, α ₁ = α _c = α ₀
= 0.3 to 0.4, and the best jitter was obtained with the strategy of β _m = 1.0. Also, Pw = 1
3 mW, Pe / Pw = 0.4 (Pe = 5 mW), Pb =
2.0 mW is the optimum recording power, and Pb / Pe = 0.
The reason for this is that the TL in FIG. 9 needs to be maintained at a somewhat high level in the recording layer of this comparative example. Even if Pb is less than 1 mW, the jitter is bad,
Even when Pb was 3 mW or more, the jitter deteriorated. Based on this pulse division method, the pulse width was adjusted to a precise _value of about 0.02 with respect to α0 according to the mark length, and the mark length dependency was measured as in Example 2. The results are shown in FIG. In addition, the linear velocity dependence during overwriting was measured. The results are shown in FIG. Regarding the linear velocity dependency, the reference clock cycle was changed according to the linear velocity so that the shortest mark length was 0.4 μm, and reproduction was always performed at 3.5 m / s. Regarding the linear velocity dependence,
The jitter after overwriting 10 times and the jitter when overwriting is performed once after DC erasure are shown. As shown in FIG. 26A, the jitter was 10% at the shortest mark length of 0.4 μm, and the jitter became sharply worse as the length became shorter. In addition, as shown in FIG. 26B, the jitter deteriorates at a recording linear velocity of 5 m / s or more. However, in the recording after DC erasure, the jitter is 2-3%.
It has fallen above. From this, the non-uniform temperature rise due to the difference in the absorption rate between the so-called crystalline state and the amorphous state,
It is considered that erasure failure or distortion of the shape of the amorphous mark occurs, and the jitter is deteriorated.

Although the jitter after overwriting at a linear velocity of 7 m / s was 20% or more, the recording after DC erasure was about 15%. Therefore, it is considered that the reason why the jitter at the time of the high linear velocity becomes high is that an appropriate pulse division method has not been selected. Originally, this recording layer has a high jitter due to coarse grains. However, at a linear velocity of 5 m / s or more, the erasure of the previous mark becomes insufficient at the time of overwriting, and the jitter with the recording after the DC erasure is reduced. The effect clearly appears as a difference from the above. In addition,
The difference in jitter between the case of overwriting the medium of Example 2 (g1) at 7 m / s and the case of recording after DC erasure was less than 0.5%. For GeTe-Sb ₂ Te ₃ pseudo binary alloy recording layer recording media using such as Ge ₂ Sb ₂ Te _5, the four-layer structure comprising protective layer / recording layer / protective layer / reflective layer, 5 to 6 m At a high linear velocity of / s or higher, recording after DC erasure is not a problem as described above, but at the time of overwriting, jitter deteriorates. For this reason, in order to reduce jitter, it is necessary to take measures such as adding an additional light absorbing layer to correct the absorptance.

Comparative Example 4 In Example 2 (g1), the recording layer was Ge _0.15 Sb _0.64 Te _0.21 . Initial crystallization is very difficult. Initializing is performed several times by initializing beam, and the jitter is measured by overwriting. % Or less was not obtained. In addition, when overwriting was repeated, the jitter increased by several% from 10 to 100 times.

Comparative Example 5 In the layer configuration of Example 2 (g1), the recording layer was Ge _0.05 Sb _0.80 Te _0.15 . 7
At m / s, α ₁ = 0.4, α _c = 0.3, β _m =
At 0.5, Pw = 14 mW, Pe / Pw = 0.5, almost the best jitter was obtained. However, the jitter was barely less than 11% after 10 times of overwriting, and 13% or more after 1000 times. It has become.

<Acceleration Test> Some of the tracks on the medium were
Using Pw = 14 mW, the EFM plus modulated random pattern was recorded by using the above-mentioned optimal pulse division method, and the jitter was measured. After that, the medium was heated to 80 ° C /
An acceleration test was performed under high temperature and high humidity of 80% RH. After 500 hours of the accelerated test, the jitter of this track was measured again. After 500 hours of the acceleration test, a random pattern was recorded on another track under the same conditions as above, and the jitter was measured. As a result, about 5% deterioration was observed, and deterioration was quick.

<Stability to reproduction light> The medium was irradiated with reproduction light at a power increased to 1.0 mW.
After 0 minute, the jitter increased by 3% and was very unstable.
In addition, the degree of modulation decreased and the marks tended to disappear.

(Embodiment 7) The medium of Embodiment 2 (a1) is changed from 1 × speed (linear velocity 3.5 m / s, reference clock cycle T = 38.2 nsec) to 2.25 × speed (7.9 m / s).
s, T = 17 nsec), α ₁ T = τ ₁ = 19
nsec, α _c T = τ _c = 11 nsec, constant at all linear velocities, and only T is inversely proportional to the linear velocity and EFM
A positive signal was recorded. Further, to determine the _{α i + β i-1 =} 1.0 constant at beta _i. Incidentally, only the final off pulse section beta _m, was changed so that the linear velocity becomes slower longer. In such a pulse division method, the reference clock cycle T
(A constant delay may be added), and _one fixed-length pulse of τ ₁ = 19 nsec (Gat
e1) and n-2 fixed-length pulses (Gate 2) with τ _c = 11 nsec may be generated, and only Gate 3 that determines the final off-pulse length may be changed according to the linear velocity, thereby simplifying the pulse generation circuit. It is preferable. Further, in this embodiment, the recording power Pw = 13.5 mW, P
Since e = 5 mW and Pb = 0.5 mW are constant,
The pulse generation circuit can be extremely simplified. Here, when the linear velocity is 5 m / s or less, Δα _i <0.47 n is satisfied, so that the thermal damage is sufficiently suppressed. In Table-5,
The values of jitter when β _m is changed at each linear velocity are summarized. In the table, “v” indicates a reference speed of 3.5 m / s. The wavelength of the pickup is 637 nm and NA = 0.63.
The jitter value itself is slightly worse than when the pulse division method is made more flexible as in the second embodiment, but a value of less than about 10% is obtained from 1 × to 2.25 × speed. Have been. Here, β ^H _m = 0.3, 1 at double speed
Assuming β ^L _m = 0.6 (point enclosed by a square) at double speed, β
It can be seen that if _m is changed in inverse proportion to the linear velocity, a jitter of less than 10% can be obtained at each linear velocity from 1 × to 2 ×. Further, in the present embodiment, although the margin of β _m is small, even if β _m = 0.2 is fixed, a jitter of less than 10% can be obtained from 1 × speed to 2.25 × speed. In this way, a pulse generation circuit that can be varied according to the linear velocity can be simplified. Further, Pb, Pb are formed on the recording medium in advance by using uneven pits or modulated groove meandering signals.
_{e / Pw, Pw, τ 0} , τ c, can be automatically determined in accordance with the linear velocity during ^{_{(β L m, β H m}} ) optimum recording condition overwriting if described.

[0210]

[Table 5]

(Embodiment 8) The layer structure was changed to the lower protective layer (Zn
S) ₈₀ (SiO ₂ ) ₂₀ having a thickness of 215 nm and a recording layer Ge
_0.05 Sb _0.69 Te _0.26 19 nm, upper protective layer (Zn
S) ₈₀ (SiO ₂ ) ₂₀ of 20 nm, reflective layer Al _0.995 T
a _0.005 was set to 200 nm. At a linear velocity of 3.5 m / s, the pulse division method is α ₁ = 0.5, α _c = 0.35, β _m =
0.5, Pw = 11 mW, Pe = 6.0 mW, Pb =
The shortest mark length (3T mark length) is changed from 0.4 μm to 0.25 μm by changing the reference clock cycle T to 0.5 mW.
m and recording was performed. T = 38.2 nsec, 0.2 μm when the mark length of the 3T mark is 0.4 μm
T at m is 19.1 nsec. The recording laser wavelength is 637 nm and NA = 0.63. Since this focused laser beam has a Gaussian distribution, it is possible to record at a higher density than the optical resolution by using only the central high temperature portion. The recording part is wavelength 432n
The reproduction was performed with a blue laser beam having m, NA = 0.6 and power of 0.5 mW. This laser light is generated from a laser light having a wavelength of about 860 nm by a nonlinear optical effect. In this layer configuration, even at 432 nm, the modulation degree is 5
A large degree of modulation of 0% or more was obtained. Further, FIG.
FIG. 8 shows the shortest mark length dependency when reproducing with the optical system of 637 nm and NA = 0.63 used for recording and when reproducing with the optical system of 432 nm and NA = 0.6. In the measurement, the set value of the equalizer is optimized as much as possible at each measurement point. In this recording medium, the shortest mark length is 0.3 μm for blue laser light reproduction.
It can be seen that good jitter of less than 13% was obtained even for m.

[0212] In the layer structure of Comparative Example 6 Example 2 (a1), the recording layer was changed to Ge _0.05 Sb _0.64 Te _0.31. Recording evaluation was performed with an optical system having a wavelength of 637 nm and NA = 0.63. At a linear velocity of 3.5 m / s, m = n-1, α ₁ =
0.4, α _c = 0.4, β _m = 0.4, Pb = 0.5 m
With W and Pe being constant at 4.5 mW, overwrite recording was performed up to ten times by changing only Pw. FIG. 27A shows the recording power dependency of the jitter at this time.
In the figure, 1 write means the first recording of an unrecorded disc,
1DOW indicates the first overwrite, and 10DOW indicates the 10th overwrite. Next, Pw = 8.
The overwrite recording was performed up to the tenth time while changing Pe only, while keeping constant at 5 mW. FIG. 27B shows the dependency of the jitter on the erasing power. In each case, good jitter was obtained in the first recording (1 write), but the jitter was sharply deteriorated by overwriting even once. It is considered that the composition of the recording layer in this comparative example is a composition richer than that of the straight line A in FIG. 3 and a sufficient erasing ratio was not obtained due to a low crystallization rate, and thus a sufficient overwriting characteristic was not obtained. Can be

Example 9 and Comparative Example 7 Example 2 (a
In the layer structure 1), the composition of the recording layer was changed as shown in Table-6. The Ge amount was changed by co-sputtering a Ge _0.05 Sb _0.73 Te _0.22 target and Ge. Using an optical system with a wavelength of 637 nm and NA = 0.63, m = n-1, Pb = 0.5 mW, β _m = 0.5
As a result, a condition in which the jitter after overwriting 10 times was minimized by changing α ₁ , α _c , Pw, and Pe was searched for. Table 6 shows the minimum jitter obtained for each recording layer composition. As the amount of Ge added increased, the jitter increased. When Ge was 10 atomic% or more, the jitter at double speed was as high as 14%. In addition, this medium was used at 80 ° C. and 80% R
When an acceleration test was performed under the condition of H, Example 9 (a) was obtained.
Examples 9 (b) and 9 (c) were slightly better than Comparative Examples. That is, the signals recorded before the acceleration test were read out after 2000 hours of the acceleration test,
In each case (c), the jitter was only degraded by about 1%. Moreover, Example 9 (a)-
The initial modulation degree of (c) was 61 to 63%, and a modulation degree of 58 to 59% was obtained even after the acceleration test for 2000 hours. The reflectance was almost unchanged at all. In particular, in Examples 9 (b) and (c), the increase was within 0.5%.

[0214]

[Table 6]

Next, Ta was added by co-sputtering a Ge _0.05 Sb _0.73 Te _0.22 target and Ta. As a result, when Ta was added to GeSbTe in an amount of 1 to 2 atomic%, the best jitter was obtained.

Example 10 and Comparative Example 8 Example 2 (g
In the layer structure of 1), the recording layer is GeS to which In is added.
bTe. In uses InS for GeSbTe target.
bTe is added by co-sputtering. The composition of each recording layer was as follows: Example 10 (a) was Ge _0.05 Sb _0.74 T
e _0.21 , Example 10 (b) was In _0.023 Ge _0.048 Sb
_0.719 Te _0.21 , Example 10 (c) shows In _0.053 Ge
_0.044 Sb _0.688 Te _0.215, Comparative Example 8 is an In _0.118 G
e _0. is a ₀₄₁ Sb _0.617 Te _0.224. FIG. 29A shows the result of evaluating the power dependency of the jitter of each medium.
(B), (c) and (d). The upper row is a recording linear velocity of 3.5 m.
/ S, the lower row shows the case of 7.0 m / s. The optical systems used were all 637 nm, NA =. 63.
When the linear velocity is 3.5 m / s, α ₁ = 0.6 and α _c = 0.3
5, β _m = 0.5, and when 7.0 m / s, α ₁ =
0.4, α _c = 0.4, and β _m = 0.5. Pb =
It was constant at 0.5 mW. Pe was fixed at two values, and only Pw was changed to measure the Pw dependency of the jitter. The Pw margin was significantly improved by the addition of the In amount of about 2 to 5 atomic%. However, when the content was more than 10 atomic%, the jitter was worse than in the case where no addition was made. In addition, the jitter after 1000 overwrites was measured in Example 10 (a).
In (c), both linear velocities were less than 10 atomic%, but in Comparative Example 8, both linear velocities were higher than 13%.

<Acceleration Test> The medium of Example 10 (b) was subjected to an acceleration test in an environment of 80 ° C./80% RH. An accelerated test was performed up to 2000 hours. The deterioration of the jitter of the signal recorded before the acceleration test was only about 1%. The initial degree of modulation was 61%, and the degree of modulation was 57% even after the acceleration test for 2000 hours. The reflectance was almost unchanged at all. The deterioration of jitter when new recording was performed on an unrecorded portion after 2000 hours was about 3%, but this is a level that does not hinder practical use at all.

(Example 11) Layer structure of Example 2 (g1)
In, the recording layer was changed to In_0.03Ge_0.05Sb_0.71Te _0.21
The disk having the groove shape shown in Table 7
A film was formed on a substrate resin substrate. In each case, the groove pitch is 0.
74 μm.

[0219]

[Table 7]

[0220] The modulation method of a wobble, the period T _w of the carrier wave is 32 times the reference data clock period T = 38.2 nsec, and a binary phase modulation. Here, the phase modulation wobble shifts the phase of the wobble wave by π in accordance with 0 or 1 of the digital data signal, as shown in FIG. That is, the frequency f _c = 1 / T _w = 1
/ (32T) unmodulated carrier (cosine or sine wave)
However, when the digital data for address is switched from 0 to 1 or from 1 to 0, the phase shifts by exactly π. Switching period T _d of the digital data 0 and 1 at low frequencies than T _w, since T _d is in a integral submultiple of T _w, be shifted phase [pi, wobble waveform varies continuously ing. A preferable point of this modulation method is that ATIP (Absolute T
Unlike frequency (FM) modulation used for ime in pregroove, since the meandering frequency is constant and the period is modulated at a high frequency of 32T, the rotation synchronization of the disk is established with reference to the wobble clock. In addition, a data clock can be directly generated in synchronization with a wobble clock. In order to change the phase by modulating digital data in this way, for example, a ring modulator as shown in FIG. 31 is used. Digital data is applied with positive and negative voltages ± V corresponding to 0 and 1. When creating a stamper master, the laser beam used to expose the photoresist is exposed while meandering in radial direction in accordance with binary phase-modulated wobble waveform voltage of ± V _w. At this time, by applying the output wave of the ring modulator to the EO modulator, the exposure beam can meander.

The following is a more detailed description. Figure period unmodulated carrier input terminal cos (2πf _c t) becomes a signal V
When _w · cos (2πf _c t) is input, V _w · cos The output of the input transformer (2πf _c t) and -V _w · c
The two carrier signal os (2πf _c t) will appear. If the digital data input is positive (+ V), and conducts D _1, D ₁ ', the carrier _{V w · cos (2πf c t} ) as it is passed through the D ₁ modulation appears at the output terminal. −V _w · cos
After the carrier of (2πf _c t) is passed through the D ₁ ', it is inverted by the output transformer _{V w · cos (2πf c t} ) , and the is summed with the output of the D ₁ passes through V _w · cos
Obtaining an output of (2πf _c t). If the digital data input is negative (-V), i.e. D _2, when D ₂ 'is conducting, the signal of _{V w · cos (2πf c t} ) is a diode D
_The modulation is guided to the lower side of the output transformer via ₂ so that the modulation is inverted at the output terminal and −V _w · cos (2π
f _c t) to become.

On the other hand, -V _w · c
os (2πf _c t) and a carrier wave diode D ₂ '
To join in the common mode input of the output transformer via, as it polarity (left _{-V w · cos (2πf c t} ))
Appears at the modulated wave output terminal. Therefore, the carrier passing through the paths of the diodes D _{2 and} D ₂ ′ is −V _w · cos (2π
synthesized a f _c t), modulation appears at the output terminal.
In the case of the ring _{modulator, V w · cos (2πf c} t) or the output terminal by the digital data input is positive or negative -
Will output a _{V w · cos (2πf c t} ). The wobble waveform modulated in this manner is input to the EO modulator, and the exposure beam can meander. In this embodiment, the wobble amplitudes are all 60 nm (peak-peak).
to-peak value). In the case of a medium in which recording is performed only in the groove, a preferable range of the groove depth is λ / (20n) = 20. 5 nm, the upper limit is λ / (10
n) = 40.8 nm. For evaluation of this medium, wavelength 6
An optical system with 37 nm and NA = 0.63 was used.

As in Embodiment 2, m = n−1, α _i + β
_i-1 = 1.0 (2 ≦ i ≦ m), α _i = α _c = constant (2 ≦
i ≦ m), a linear velocity of 3.5 m /
In s, α _i = 0.5, α _c = 0.3, β _m =
0.5, Pw = 13 mW, Pe = 6 mW, linear velocity 7 m
/ S, α ₁ = 0.4, α _c = 0.35, β _m
= 0.5, Pw = 14 mW, Pe = 7 mW. First, recording was performed in the groove at a linear velocity of 3.5 m / s, and Rt
The op and the degree of modulation were measured. In addition, 3.5m / s and 7
The jitter of the recording signal was measured at m / s. The results are shown in Table-8.

[0224]

[Table 8]

First, Example 11 (k) has a depth of 18 nm.
, But a push-pull signal could hardly be detected and tracking servo could not be applied. In addition, it is very difficult to form such a shallow groove evenly in terms of stamper preparation, and in practice, very large unevenness was observed in the tracking servo signal. FIGS. 32A and 32B show the dependence of the modulation degree and Rtop on the groove shape. In Examples 11 (h) to 11 (j), grooves having a depth of 42 nm are provided, but the reflectivity is significantly reduced as compared with the case of a depth of 27 nm, which is not preferable because it is reduced by 5% or more. The degree of modulation decreases particularly when the groove is narrow, and at a width of 0.23 μm,
Even at a depth of 35 nm, the degree of modulation was significantly reduced. In this embodiment, the layer structure is the same. However, if the layer structure has a high reflectivity in order to compensate for a decrease in the reflectivity in the case of a depth of 42 nm, the decrease in the degree of modulation becomes more remarkable. That is, a groove having a depth of 42 nm is not suitable for recording in the groove. Groove depth 4
If the groove width is less than 0.3 μm, the wobble signal significantly leaks into the recording data signal when the groove width is less than 0.3 μm. Compared to when the groove width is 0.3 μm or more, jitter deteriorates by 1% or more at a linear velocity of 3.5 m / s, and 2-3% at a linear velocity of 7 m / s.
Also gets worse.

(Example 12) The layer structure was changed to the lower protective layer (Z
nS) ₈₀ (SiO ₂ ) ₂₀ with a film thickness of 65 nm and a recording layer Ge
16 nm of _0.05 Sb _0.73 Te _0.22 , upper protective layer (Zn
S) ₈₀ (SiO ₂ ) ₂₀ of 20 nm, first reflective layer Al
_The thickness of _0.995 Ta _0.005 was 40 nm, and the thickness of the second reflective layer Ag was 70 nm. From the lower protective layer to the first reflective layer, the first reflective layer is formed by a sputtering method without releasing the vacuum. A film was formed. After forming the second reflective layer, an ultraviolet curable resin was laminated as an overcoat layer by 4 μm by spin coating. Two of the resulting disks were bonded together so that the overcoat layers faced each other. The first reflective layer was formed at an ultimate vacuum of 4 × 10 ⁻⁴ Pa or less and an Ar pressure of 0.55 Pa. The volume resistivity was 55 nΩ · m. Impurities such as oxygen and nitrogen were less than the detection sensitivity in X-ray excitation photoelectron spectroscopy, and were considered to be less than about 1 atomic% in total. The deposition of the second reflective layer is performed at a degree of ultimate vacuum of 4 × 10 ^−4.
The test was performed at an Ar pressure of 0.35 Pa or less under Pa. The volume resistivity was 32 nΩ · m. Impurities such as oxygen and nitrogen are less than the detection sensitivity in X-ray excitation photoelectron spectroscopy,
It was considered to be less than atomic%. Wavelength 637 nm, NA
Using an optical system of 0.60, a linear velocity of 3.5 m / s, α ₁
= 0.4, α _c = 0.35, β _m = 0.5 When the jitter was measured after overwriting 10 times using the pulse division method, Pw = 11 mW, Pe = 6.0 mW, Pb
= 0.5 mW, a minimum jitter of 6.5% was obtained. After the medium was left under high temperature and high humidity of 80 ° C. and 80% RH for 500 hours, recording was performed in the same manner, and no deterioration was observed.

(Example 13) A stamper having a wobble spiral groove having a groove pitch of 0.74 µm, a groove width of 0.3 µm, and a groove depth of 40 nm was prepared.
A polycarbonate resin substrate having a diameter of 120 mm and a thickness of 0.6 mm was formed by injection molding. As shown in Table-9, 36 mm from a radius of 22.5 mm to 58.5 mm
Is a recording area, and the recording area is divided into 255 bands (zones). Each band contains 191 tracks. Since the band width is set so that the end of each band is exactly at the 191st track, each band width is exactly 36
/ 255. For this reason, the outermost end of the recording area is 58.54 mm. The channel bit length is 0.
At a linear velocity of 3.49 m / s, a reference clock of 26.16 MHz (T = 38.23 nsec) is obtained. The wobble period was set to be 9 times the channel bit length at the center radius of each band. Its physical period is 1.2 μm. First, the total number of channel bits and the total number of wobbles at the center radius of each band are calculated so that the number of channel bits or the number of wobbles included in one round in the same band is constant.

As shown in Table 9, at the beginning and end of the band, ±
The number of channel bits or wobbles is constant with 1% accuracy. That is, recording with a constant linear density can be performed in the ZCAV system, which is the same as that in the CLV system, and the specification of the read-only DVD is sufficiently satisfied. From the above premise, when the disk is rotated so that a linear velocity of 3.49 m / s is obtained at the center radius of each band, the wobble cycle is exactly equal to the reference clock cycle of DVD data T = 38.23 ns.
9 times of c. This medium is rotated so that the linear velocity becomes 3.49 m / s at the band center radius of the innermost peripheral band in Table 9, and used as a ZCAV system medium.
The period of the carrier wave is reproduced from the wobble of each band in the CAV rotation and times 1/9, to generate data reference clock T _q in each band, EFM based on the clock
The recording of the plus-modulated data is performed. At the time of reproduction, if the rotation synchronization is achieved so that the data reference clock frequency generated from the recorded data becomes 26.16 MHz as described below, the variation of the channel bit length in each zone is less than ± 1%. Thus, reproduction in the CLV mode can be performed substantially without any trouble.

That is, the reference clock 26.16M
Hz (T = 38.23 nsec) is generated by a crystal oscillator, this phase is compared with a data reference clock generated from recorded data, and a normal PLL (Phase Locked Loop) is used so that both are synchronized. Fine-tune the rotation speed by the control method. Such rotation control by PLL control is currently performed in DVD-ROM reproduction, and is useful in that the method can be applied as it is.

[0230]

[Table 9]

[0231]

[Table 10]

(Example 14) In the layer structure of Example 2 (a1), the reflection layer was made of Al _0.975 Ta _0.025 . The volume resistivity was 220 nΩ · m. A plurality of samples were prepared by changing the film thickness from 200 nm to 400 nm.
In the same manner as in the measurement of FIG. 10, jitter measurement was performed using the optimum pulse division method in FIG. Film thickness 3
The best jitter of 12% was obtained around 00 nm. Even if the reflective layer was made thicker or thinner, only worse jitter was obtained.

Example 15 In the layer structure of Example 11 (a), the thickness of the upper protective layer was set to 23 nm. In-groove recording was performed on this medium. Wavelength 405 nm, NA = 0.6
5 optical system, almost circular and spot diameter about 0.5μ
m (diameter at 1 / e ² intensity of a Gaussian beam) was generated, and recording / reproduction was performed through a 0.6 mm thick substrate. At a linear velocity of 4.86 m / s, an EFM-plus-modulated signal with the shortest mark (3T mark) length of 0.25 μm was recorded. By the same recording pulse division method as in the second embodiment, m = n-1, α ₁ = 0.5, α _c = 0.38, β _m
= 0.67, Pw = 9.5 mW, Pb = 0.5 m
When overwriting was performed 10 times at W, Pe = 4.0 mW, the jitter was 10%. It was found that higher quality recording was possible by recording / reproducing with a blue laser than in the case of Example 7. Further, even with a medium designed for the current red laser, recording and reproduction can be performed with the blue laser as it is to increase the density.

(Example 16) Layer structure of Example 2 (a1)
In the above, the recording layer was Ga_0.05Ge_0.05Sb_0.68Te _0.22
A medium was prepared. Initialization is the same as in Example 2 (a1).
I went. For the measurement, wavelength 637 nm, NA = 0.6
The optical system No. 3 was used. The length of the shortest mark 3T is 0.4μ
m, and the linear velocity is 3.5 m / s.
I went in. With the same recording pulse strategy as in Example 2,
m = n-1, α_i+ Β_i-1= 1.0 (2 ≦ i ≦ m), α
_i= Α_c= Constant (2 ≦ i ≦ m), α₁= 0.5, α
_c= 0.3, β_m= 0.5, Pw = 13.5 mW,
Pe = 6.0mW, Pb = 0.5mW, Overlap
The site properties were evaluated. Initial recording (non-overwriting),
10 overwrites, 100 overwrites, 10
After overwriting 00 times, the jitter was 6.9%,
6.7%, 7.0% and 7.3% were good. Further
Similarly, at a linear velocity of 7.0 m / s, α₁= 0.4, α_c
= 0.35, β_m= 0.5, Pw = 14.0 mW,
Pe = 7.0 mW, Pb = 0.5 mW, overlay
The site properties were evaluated. Initial recording (non-overwriting),
10 overwrites, 100 overwrites, 10
After overwriting 00 times, the jitter was 7.4%,
7.7%, 8.0% and 8.5% were good. Modulation depth
In each case, a value of 55 to 60% was obtained. This medium is 80
Leave for 1000 hours in accelerated test environment of ℃ / 80% RH
A record was then made before the test. Before the accelerated test
The deterioration of the signal jitter was less than 1%. Also, modulation
As for the degree, a value of 52 to 57% was obtained.

(Embodiment 17) As in Embodiment 2, 0.6
Pitch 0.74 on polycarbonate resin substrate with mm thickness
A wobble groove of μm is formed, and reflection is performed as shown in FIG.
A layer, a second protective layer, a recording layer, and a first protective layer were formed in this order.
Reflective layer Al_0.995Ta_0.005Is a film thickness of 165 nm,
Protection layer (ZnS)₈₀(SiO_Two)₂₀Indicates a film thickness of 20 nm and was recorded.
Layer In_0.03Ge_0.05Sb_0.70Te_0.22To a film thickness of 16 nm,
First protective layer (ZnS)₈₀(SiO_Two)₂₀To a film thickness of 68 n
m, each of which was formed by a sputtering method. Its
And a glass plate having a thickness of 0.6 mm facing the first protective layer.
Was adhered. Initialization is performed through a glass substrate by 500
Irradiate a laser beam of about mW at a linear velocity of 5 m / s and perform
Was. Through this glass substrate, a wavelength of 637 nm, NA =
The recording layer was irradiated with laser light using the optical system of 0.6.
Recorded and played back. The recording is uneven when viewed from the laser incident side.
Went to the far side of. This corresponds to the inside of the groove in the second embodiment.
EFM Plus with the shortest mark 3T length of 0.4 μm
The modulation signal was performed at a linear velocity of 3.5 m / s. Example 2 and
M = n−1, α in a similar recording pulse strategy_i+ Β
_i-1= 1.0 (2 ≦ i ≦ m), α_i= Α_c= Constant (2 ≦
i ≦ m) and α₁= 0.9, α_c= 0.35, β_m=
0.5, Pw = 12.0 mW, Pe = 6.0 mW,
With Pb = 0.5 mW, the overwrite characteristics were evaluated.
Was. After 10 overwrites, the jitter is 10.5%,
The degree of modulation was 61%. Furthermore, a linear velocity of 7.0 m / s
Similarly, α₁= 0.55, α_c= 0.40, β _m=
0.5, Pw = 13.0 mW, Pe = 5.5 mW,
With Pb = 0.5 mW, the overwrite characteristics were evaluated.
Was. After 10 overwrites, the jitter is 11.2%,
The degree of modulation was 61%.

[0236]

According to the present invention, overwrite can be performed at a high speed, mark edge jitter can be reduced, and high-density mark length modulation recording can be performed. A good optical information recording medium can be obtained. In addition, by selecting an appropriate recording layer composition and layer configuration, a phase-change optical recording medium having excellent reproduction compatibility with a read-only medium and having high repeated overwrite durability can be obtained. More specifically, it has playback compatibility with a so-called DVD disc, and can perform one-beam overwriting in a wide linear velocity range including a standard playback speed of 3.5 m / s to a double speed of 7 m / s. It is possible to provide an optical information recording medium and an optical recording method which can be used for a rewritable DVD disk and which does not show deterioration even after overwriting over 10,000 times. Further, since the medium of the present invention has a wide linear velocity margin,
Even when recording is performed by rotating the medium at a constant angular velocity, such as the AV method or the ZCAV method, it is possible to overcome the problem of the difference in recording characteristics due to the difference in linear velocity between the inner and outer circumferences of the medium. If the CAV method is adopted, it is not necessary to change the disk rotation speed for each radial position, and the access time can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an amorphous mark shape.

FIG. 2 is a diagram illustrating a change in reflectance when recording is performed on a medium according to an example of the invention.

FIG. 3 shows GeS indicating the composition range of the recording layer of the medium of the present invention.
bTe ternary phase diagram.

FIG. 4 shows a conventional GeSbTe composition range.
Te ternary phase diagram.

FIG. 5 is a schematic view showing an example of a layer configuration of a medium of the present invention.

FIG. 6 is a signal waveform diagram showing the relationship between signal strength, signal amplitude, and modulation.

FIG. 7 is a graph for explaining the dependency of the reflectance on the thickness of the first protective layer.

FIG. 8 is a diagram showing an example of a pulse division method in a power ternary modulation recording system.

FIG. 9 is a schematic diagram for explaining a time change of the temperature of the recording layer.

FIG. 10 is a diagram showing an example of a pulse division method of a power ternary modulation recording method suitable for mark length modulation recording.

FIG. 11 is a diagram for realizing the pulse division method of FIG.
FIG. 3 is a conceptual diagram illustrating timings of three types of gate generation circuits.

FIG. 12 is a graph showing the reproduction light power dependence of jitter in Example 1 and Comparative Example 1.

FIG. 13 is a graph showing the dependency of the jitter on the recording pulse division method in the first embodiment.

FIG. 14 is a graph showing the dependence of jitter on the recording pulse division method in the first embodiment.

FIG. 15 is a graph showing recording power dependence of jitter, reflectance, and modulation in Example 2.

FIG. 16 is a graph showing the dependency of the number of repetitive overwrites on the jitter, reflectance, and degree of modulation in Example 2.

FIG. 17 is a graph showing mark length dependence of jitter in Example 2 (g1) and Example 2 (d2).

FIG. 18 is a graph showing the dependency of the jitter on the tilt angle of the substrate in Example 2.

FIG. 19 is a graph showing α ₁ and α _c dependence of jitter after ten times overwriting in Example 4.

FIG. 20 is a graph showing the dependence of jitter, Rtop, and modulation factor on the number of repeated overwrites in Example 4.

FIG. 21 (a) Dependence of jitter on pulse division method in Example 6, (b) Dependency of jitter on write power,
And (c) a graph showing the write power dependence of Rtop and modulation after 10 overwrites.

FIG. 22 is a graph showing the dependence of jitter, Rtop, and modulation factor on the number of repeated overwrites in Example 6.

FIG. 23 is a graph showing mark length dependency of jitter in Example 6.

FIG. 24 (a) Dependence of jitter on pulse division method in Comparative Example 2, (b) Dependence of jitter on write power,
And (c) a graph showing the write power dependence of Rtop and modulation after 10 overwrites.

FIG. 25 is a diagram showing a pulse division method of the recording method used in Comparative Example 3.

FIG. 26 is a graph showing the mark length dependency and the linear velocity dependency of jitter in Comparative Example 3.

FIG. 27 is a graph showing the dependency of jitter on Pw and Pe in Comparative Example 6.

FIG. 28 is a graph showing the dependency of jitter on the shortest mark length in Example 8.

FIG. 29 is a graph showing Pw dependence of jitter in Example 10 and Comparative Example 8.

FIG. 30 is a view for explaining the relationship between a digital data signal and a wobble waveform.

FIG. 31 is a view for explaining a mechanism for modulating a wobble waveform by a digital data signal.

FIG. 32 is a graph showing the groove width dependence of the modulation degree and Rtop in Example 11.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G11B 7/24 538 G11B 7/24 538E 538F 561 561 561M 563 563A B41M 5/26 C01G 17/00 C01G 17/00 G11B 7 / 00 631A G11B 7/00 631 B41M 5/26 X (72) Inventor Towa Horie 1000 Kamoshita-cho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Chemical Corporation Yokohama Research Laboratory F-term (reference) 2H111 EA04 EA12 EA23 EA31 EA32 EA37 EA40 EA43 FA01 FA11 FA12 FA14 FA23 FA39 FB04 FB05 FB06 FB07 FB09 FB12 FB15 FB16 FB17 FB19 FB21 FB22 FB23 FB24 FB25 FB27 FB30 5D029 JA01 JB35 JC17 LA13 LA19 LB07 LB11 MA17 WA14 WB11 MA17 WA14 WC11 BB05 CC02 CC14 DD02 EE05 FF15 FF25 GG03 GG07 GG28 KK03 KK05 LL01

Claims (65)

[Claims] 1. A semiconductor device comprising a substrate having at least a phase-change recording layer on a substrate, wherein a crystal part of the recording layer is in an unrecorded / erased state, an amorphous part is in a recorded state, and a plurality of recording layers having a minimum mark length of 0.5 μm or less. An optical information recording medium for recording information according to a recording mark length, wherein recrystallization in which erasure substantially proceeds by crystal growth from a boundary between an amorphous portion or a molten portion and a peripheral crystal portion. An optical information recording medium characterized in that the medium is recorded by optical discs. 2. The phase-change recording layer according to claim 1, wherein said phase-change recording layer is made of
2. The optical information recording medium according to claim 1, comprising a thin film containing e as a main component. Wherein the phase change type recording layer, M _y (Sb _x T
e _1-x ) _1-y (0.6 ≦ x ≦ 0.9, 0 <y ≦ 0.2,
M is Ga, Zn, Ge, Sn, In, Si, Cu, A
u, Ag, Al, Pd, Pt, Pb, Cr, Co, O,
2. The optical information recording medium according to claim 1, comprising a thin film mainly containing an alloy of at least one of S, Se, Ta, Nb, and V). 4. A phase change type recording layer comprising a thin film containing Ge, Sb, and Te as main components on a substrate, wherein a crystal part of the recording layer is in an unrecorded / erased state and an amorphous part is recorded. An optical information recording medium for recording information with a plurality of recording mark lengths having a minimum mark length of 0.5 μm or less, wherein the recording layer is sufficient to melt the recording layer at a constant linear velocity. When the recording light of the recording power Pw is continuously irradiated, the recording layer is substantially crystallized, and at a constant linear velocity, the recording power P sufficient to melt the recording layer is obtained.
An optical information recording medium, wherein an amorphous mark is formed when the recording light is irradiated and then cut off. 5. The optical information recording medium according to claim 1, wherein when a signal is recorded with a plurality of mark lengths having a minimum mark length of 0.5 μm or less, the signal is reproduced immediately after the recording. If the modulation degree of the signal is M ₀ and the modulation degree of the signal reproduced after 1000 hours has elapsed under the conditions of 80 ° C. and 80% RH after recording is M ₁ , M ₁ / M ₀ ≧ 0. 9. An optical information recording medium according to item 9. 6. The optical information recording medium according to claim 1, wherein a plurality of mark lengths each having a shortest mark length of 0.4 μm are used.
When a random signal of the M plus modulation method is recorded, the modulation degree of the signal reproduced immediately after recording is defined as M _0, and after recording, the modulation degree of the signal reproduced after 1000 hours has elapsed under the conditions of 80 ° C. and 80% RH. When M _1, Equation 2] M ₁ / M optical information recording medium is ₀ ≧ 0.9. 7. A substrate is provided with a first protective layer, a phase-change recording layer, a second protective layer, and a reflective layer in this order from the incident direction of recording / reproducing light. An optical information recording medium for recording information with a plurality of recording mark lengths having a minimum mark length of 0.5 μm or less in a recording / erasing state and an amorphous portion in a recording state, wherein a phase change recording layer is When the film thickness is 5 nm or more and 25 nm or less,
In the eSbTe ternary phase diagram, a straight line A connecting (Sb _0.7 Te _0.3 ) and Ge, (Ge _0.03 Sb _0.68 Te _0.29 ) and (Sb _0.95 Ge _0.05 )
, A straight line B connecting (Sb _0.9 Ge _0.1 ) and (Te _0.9 Ge _0.1 ), and a straight line D connecting (Sb _0.8 Te _0.2 ) and Ge. An optical information recording medium comprising a thin film mainly composed of a GeSbTe alloy having a composition (not including on a line) and a second protective layer having a thickness of 5 nm or more and 30 nm or less. 8. The recording layer has a straight line A connecting (Sb _0.7 Te _0.3 ) and Ge in the ternary phase diagram of GeSbTe, (Ge _0.03 Sb _0.68 Te _0.29 ) and (Sb _0.9 Ge _0.1 ).
B ′, a straight line C connecting (Sb _0.9 Ge _0.1 ) and (Te _0.9 Ge _0.1 ), and a straight line D connecting (Sb _0.8 Te _0.2 ) and Ge. 8. The optical information recording medium according to claim 7, comprising a thin film mainly composed of a GeSbTe alloy having a composition (not including on a boundary line). 9. The recording _{layer, Ge x (Sb y Te 1} -y)
Thin film mainly composed of _1-x alloy (0.04 ≦ x <0.1
8. The optical information recording medium according to claim 7, wherein 0, 0.72 ≦ y <0.8). 10. A recording _{layer, Ge x (Sb y Te 1} -y)
Thin film mainly composed of _1-x alloy (0.045 ≦ x ≦ 0.0
75. The optical information recording medium according to claim 7, comprising: 0.74 ≦ y <0.8). 11. The recording layer further contains at least one element selected from O, N, and S, and the total content of these elements is 0.1 atomic% or more and 5 atomic% or less. 11. The optical information recording medium according to any one of 7 to 10. 12. The recording layer further comprises V, Nb, T
a, containing at least one element selected from Cr, Co, Pt, and Zr, wherein the total content of these elements is 8 atomic% or less, and the total content of these elements and Ge is 15 atomic% or less The optical information recording medium according to any one of claims 7 to 10, wherein 13. The recording layer according to claim 1, further comprising Al, In,
And at least one element selected from Ga and Ga, wherein the total content of these elements is 8 atomic% or less, and the total content of these elements and Ge is 15 atomic% or less. The optical information recording medium according to any one of the above. 14. The recording layer has a thickness of 10 nm or more and 20 n or more.
14. The optical information recording medium according to claim 7, wherein m is equal to or less than m. 15. The second protective layer has a thickness of 10 nm or more and 2
15. The optical information recording medium according to claim 7, which has a thickness of 5 nm or less. 16. A medium for recording or reproducing information by entering recording / reproducing light through a substrate, wherein the first protective layer has a thickness of 50 nm or more. Optical information recording medium. 17. The reflective layer has a thickness of 40 nm to 300 nm.
nm or less, the volume resistivity is 20 nΩ · m or more and 150 nΩ.
The optical information recording medium according to any one of claims 7 to 16, wherein m is equal to or less than m. 18. The reflective layer has a thickness of 150 nm or more and 30 or more.
0 nm or less, Ta, Ti, Co, Cr, Si, Sc,
A containing at least one of Hf, Pd, Pt, Mg, Zr, Mo and Mn in an amount of 0.2 atomic% or more and 2 atomic% or less
18. The optical information recording medium according to claim 17, comprising an 1 alloy. 19. The reflective layer has a thickness of 40 nm to 150 nm.
nm, Ti, V, Ta, Nb, W, Co, Cr,
Si, Ge, Sn, Sc, Hf, Pd, Rh, Au, P
18. The optical information recording medium according to claim 17, comprising an Ag alloy containing at least one of t, Mg, Zr, Mo, and Mn at 0.2 atomic% or more and 5 atomic% or less. 20. The reflective layer is a multilayer reflective layer comprising a plurality of metal films, and at least 50% of the total thickness of the multilayer reflective layer has a volume resistivity of 20 nΩ · m to 150 nΩ · m. 20. The optical information recording medium according to any one of claims to 19. 21. A film having a thickness of 5n between the second protective layer and the reflective layer.
21. The optical information recording medium according to claim 17, further comprising an interface layer having a thickness of at least 100 nm. 22. A film having a thickness of 1 n between the second protective layer and the reflective layer.
and an interface layer having a thickness of not less than 100 nm and not more than 100 nm, wherein the interface layer is made of Ta, Ti, Co, Cr, Si, Sc, H
f, Pd, Pt, Mg, Zr, Mo and Mn, made of an Al alloy containing at least 0.2 atomic% and not more than 2 atomic%, wherein the reflective layer is made of Ti, V, Ta, Nb, W , Co, Cr, S
i, Ge, Sn, Sc, Hf, Pd, Rh, Au, P
18. The optical information recording medium according to claim 17, comprising an Ag alloy or Ag containing at least one of t, Mg, Zr, Mo, and Mn at 0.2 atomic% or more and 5 atomic% or less. 23. The method according to claim 19, wherein the Al layer is provided between the interface layer and the reflective layer.
A layer consisting of an alloy and / or an Ag alloy oxide is present,
23. The optical information recording medium according to claim 22, wherein the thickness of the oxide layer is 1 nm or more and 10 nm or less. 24. The optical information recording medium according to claim 7, wherein a track on which information is recorded has a pitch of 0.8 μm or less. 25. A medium for recording information with only a groove inside as a track, having a groove with a pitch of 0.8 μm or less on a substrate, a reproducing light wavelength of λ, and a refractive index of the substrate at that wavelength. 25. The optical information recording medium according to claim 24, wherein n is a groove depth in a range of λ / (20n) to λ / (10n). 26. A light source for recording and reproducing data, wherein light having a wavelength of 630 to 670 nm passes through an objective lens having a numerical aperture NA of 0.6 to 0.65 and is condensed on a recording layer via a substrate. A medium, wherein the groove has a groove pitch of 0.6 to 0.8 μm and a groove depth of 25.
溝 40 nm, the groove width is 0.25 to 0.5 μm, and the groove has a meander of a period of 30 to 40 times the data reference clock period T, and the amplitude of the meander (peak-to-p).
The optical information recording medium according to claim 25, wherein the peak value (eak value) is 40 to 80 nm. 27. A medium for recording information with both tracks inside and between grooves as tracks, having a groove on a substrate, a reproduction light wavelength of λ, and a refractive index of the substrate at that wavelength of n. The groove depth is λ / (7n) to λ / (5n) or λ / (3.5n) to λ / (2.5n), and the groove width GW and the groove width LW are both 0. 2μm or more 0.4μ
m or less, and the GW / LW ratio is 0.8 or more and 1.2
25. The optical information recording medium according to claim 24, wherein: 28. The optical information recording medium according to claim 1, wherein an erasing power P capable of crystallizing an amorphous material between recording marks.
e, and the time length of one recording mark is nT (T
Reference clock period, n is an integer of 2 or more), the time length nT of the recording mark, Equation 3] _{η 1 T, α 1 T,} β 1 T, α 2 T, β 2 T, ·
.., Α _i T, β _i T,..., Α _m T, β _m T, η ₂ T (where m is the number of pulse divisions, m = nk, and k is 0 ≦ k)
≤2. Also, Σ _i (α _i + β _i ) + η ₁
+ Η ₂ = n, η ₁ is a real number satisfying η ₁ ≧ 0, η ₂ is η ₂
A real number satisfying ≧ 0, and 0 ≦ η ₁ + η ₂ ≦ 2.0. α
_i (1 ≦ i ≦ m) is a real number satisfying α _i > 0, and β _i (1 ≦ m)
i ≦ m) is a real number satisfying β _i > 0, and Σα _i <0.5n. α ₁ = 0.1 to 1.5, β ₁ = 0.3 to 1.0,
β _m = 0 to 1.5, α _i = 0.1 to 0.8 (2 ≦ i
≦ m). Note that α _i + for i where 3 ≦ i ≦ m.
β _i-1 is in the range of 0.5 to 1.5 and is constant regardless of i. Divided in the order of) irradiated with recording light barrel Pw ≧ Pe becomes recording power Pw to melt the recording layer is in the _{α i T (1 ≦ i ≦} m) of _{time, β i T (1 ≦ i} ≦ Within time m), 0
<Pb ≦ 0.2Pe (However, in β _m T, 0 <
An optical information recording medium for performing recording by irradiating a recording light with a bias power Pb of (Pb ≦ Pe). 29. The optical information recording medium according to claim 28, wherein light having a wavelength of 350 to 680 nm and a numerical aperture NA of 0.5 are provided.
When condensing light on the recording layer through an objective lens of 5 to 0.9 and performing data recording and reproduction, m = n-1 or m = n-2, α ₁ = 0.3 to 1.5, α ₁ ≧ α _i = 0.2 to 0.8 (2 ≦ i ≦ m), α _i + β _i−1 = 1.0 (3 ≦ i ≦ m), 0 ≦ Pb ≦ 1.5 (mW), 0.3 An optical information recording medium for performing recording with ≦ Pe / Pw ≦ 0.6. 30. The optical information recording medium according to claim 28, wherein a light having a wavelength of 600 to 680 nm and a numerical aperture NA of 0.5.
When recording / reproducing data with the shortest mark length in the range of 0.35 to 0.45 μm through the objective lens of 5 to 0.65 and focusing on the recording layer through the substrate, n is 1 to 14 M = n-1, Pb is constant irrespective of the linear velocity, Pe / Pw is variable in the range of 0.4 to 0.6 depending on the linear velocity, and (i) recording In the linear velocity range of 3 to 4 m / s, the reference clock cycle T is To, α ₁ = 0.3 to 0.8, α ₁ ≧ α _i = 0.2 to 0.4, and Constant (2 ≦ i ≦ m), α ₂ + β ₁ ≧ 1.0, α _i + β _i−1 = 1.0 (3 ≦ i ≦ m), β _m = 0.3 to 1.5, α _The recording power P within the time of _i T (1 ≦ i ≦ m)
irradiating the recording light of w _1, (ii) recording linear velocity 6-8 m /
In the range of s, the reference clock cycle T is To / 2, α ′ ₁ = 0.3 to 0.8, α ′ ₁ ≧ α ′ _i = 0.3 to 0.5, and regardless of i Constant (2 ≦ i ≦ m), α ′ _i + β ′ _i−1 = 1.0 (3 ≦ i ≦ m), β ′ _m = 0 to 1.0, α _i T (1 ≦ i ≦ m) Recording power P
when the irradiation with recording light of _{w 2, α 'i> α} i (2 ≦ i ≦ m), and, 0.8 ≦ Pw ₁ /
An optical information recording medium for recording with Pw ₂ ≦ 1.2. 31. The optical information recording medium according to claim 28, further comprising a predetermined recording area, wherein the linear velocity at the innermost circumference of the recording area is 2 to 4 m / s, and at the outermost circumference of the recording area. The medium is rotated at a constant angular velocity so that the linear velocity becomes 6 to 10 m / s. The recording area is composed of a plurality of zones separated by a radius, and the recording density is substantially changed according to the average linear velocity in each zone. When performing recording by changing the reference clock period T so as to be constant, m is constant regardless of the zone, and Pb / Pe and / or α _i (i is 1 ≦ from the outer zone toward the inner zone). an optical information recording medium for performing recording by monotonously decreasing at least one of i ≦ m). 32. The optical information recording medium according to claim 31, wherein the recording area is divided into p zones by a radius,
The innermost side is a first zone, the outermost side is a p-th zone, an angular velocity in a q-th zone (q is an integer of 1 ≦ q ≦ p) is ω _q , and an average linear velocity is <v _q > _ave , If the maximum linear velocity is <v _q > _max , the minimum linear velocity is <v _q > _min , the reference clock cycle is T _q , and the time length of the shortest mark is n _min T _q , <v _p > _ave / <v _{1> ave} is in the range of _{1.2~3, <v q> max /} <v q> min is 1.5 or less,
(I) Within the same zone, ω _q , T _q , α _i , β _i , P
e, Pb, and Pw are constant, the physical length of the shortest mark n _min T _q <v _q > _ave is 0.5 μm or less;
T _q <v _q > _ave is substantially constant for all q satisfying 1 ≦ q ≦ p, and m = n−1 or m = n−2, α ₁ = 0.3 to 1.5, α ₁ ≧ α _i = 0.2 to 0.8 (2 ≦ i ≦ m), α _i + β _i−1 = 1.0 (3 ≦ i ≦ m), 0 ≦ Pb ≦ 1.5 (mW), 0.4 ≦ Pe / Pw ≦ 0.6, (ii) Pb, Pw, Pe / Pw, α _i (1 ≦ i ≦ m) for each zone,
β ₁ and β _m are variable, and optical recording for performing recording by monotonously decreasing at least α _i (i is at least one of 2 ≦ i ≦ m) from the outer peripheral zone toward the inner peripheral zone. Information recording medium. 33. The maximum value of Pw in the recording area is P
When you w _max, the minimum value and Pw _min, Pw _max / Pw
_33. The optical information recording medium according to claim 32, wherein _min ≦ 1.2. 34. The optical information recording medium according to claim 31, wherein light having a wavelength of 600 to 680 nm and a numerical aperture NA of 0.5 are provided.
When recording and reproducing data by condensing light on a recording layer through a substrate through a 5-0.65 objective lens, the innermost circumference of the recording area is in a range of a radius of 20 to 25 mm, and the outermost circumference is The radius is in the range of 55 to 60 mm, the average linear velocity in the innermost zone is 3 to 4 m / s, the angular velocity in the q-th zone (where q is an integer of 1 ≦ q ≦ p) is ω _q , The linear velocity is <v _q > _ave , the maximum linear velocity is <v _q > _max , the minimum linear velocity is <v _q > _min , the reference clock cycle is T _q , and the time length of the shortest mark is n _min T _q.
Then, n is an integer of 1 to 14, m = n−1, ω _q , Pb and Pe / Pw are constant regardless of the zone, and T _q <v _q > _ave is 1 ≦ q ≦ It is substantially constant for all q of p, and ## EQU4 ## (<v _q > _max− <v _q > _min ) / (<v _q >
_{max + <v q> min)} < meets 10%, (i) in the first _{^{zone, α 1 1 = 0.3~0.8, α}} 1 1 ≧ α 1 i = 0.2~0.4 constant irrespective of i a is (2 ≦ i ≦ m), α 1 2 + β 1 1 ≧ 1.0, and ^{_{α 1 i + β 1 i-}} 1 = 1.0 (3 ≦ i ≦ m), (ii ) in the first p zone, constant regardless of the alpha ^p ₁ = 0.3 to 0.8, a ^{_{α p 1 ≧ α p i =}} 0.3~0.5 i (2 ≦ i ≦ m), When α ^p _i + β ^p _i−1 = 1.0 (2 ≦ i ≦ m),
(Iii) In other zones, α ¹ _i ≦ α ^q _i ≦ α
_{^{p i (2 ≦ i ≦ m}} ) and then, alpha ^q ₁ optical information recording medium for recording is by a value between the alpha ¹ ₁ and alpha ^p _1. 35. ^{_{α 1 1 ≧ α q 1 ≧}} α p 1 ( provided that, alpha ¹ ₁
> Α ^p ₁ ) for recording.
5. The optical information recording medium according to item 4. 36. Pb, Pe / Pw, β ₁ , and β _m are constant irrespective of the zone, and a request for recording by changing α ₁ and α _i (2 ≦ i ≦ m) depending on the zone. Item 34. The optical information recording medium according to Item 34 or 35. 37. At least Pe / Pw, Pb, Pw,
β_m, (Α¹ ₁, Α^p ₁), (Α¹ _c, Α^p _c) Number
However, pre-pit rows or groove deformation on the substrate in advance
Claim 34.
Optical information recording medium. 38. By deforming the pre-pit row or groove,
38. An optical information recording medium in which address information is recorded on a substrate in advance, the information including, in addition to the address information, information on appropriate α ₁ and α _i (2 ≦ i ≦ m) in the address. The optical information recording medium according to any one of the above. 39. The optical information recording medium according to claim 1, wherein an erasing power P capable of crystallizing an amorphous material between recording marks.
e, and the time length of one recording mark is nT (T
Is the reference clock cycle, n is an integer of 2 or more), and the temporal length nT of the recording mark is expressed as follows: η ₁ T, α ₁ T, β ₁ T, α ₂ T, β ₂ T,.
.., Α _i T, β _i T,..., Α _m T, β _m T, η ₂ T (where m is the number of pulse divisions, m = nk, and k is 0 ≦ k)
≤2. Also, Σ _i (α _i + β _i ) + η ₁
+ Η ₂ = n, η ₁ is a real number satisfying η ₁ ≧ 0, η ₂ is η ₂
A real number satisfying ≧ 0, and 0 ≦ η ₁ + η ₂ ≦ 2.0. α
_i (1 ≦ i ≦ m) is a real number satisfying α _i > 0, and β _i (1 ≦ m)
i ≦ m) is a real number satisfying β _i > 0. α ₁ = 0.1 ~
1.5, β ₁ = 0.3 to 1.0, β _m = 0 to 1.5, α _i is in the range of 0.1 to 0.8 at 2 ≦ i ≦ m, and It is constant regardless of i. Note that 3 ≦
In the case of i ≦ i, α _i + β _i−1 is in the range of 0.5 to 1.5, and is constant regardless of i. Divided in the order of) irradiated with recording light barrel Pw ≧ Pe becomes recording power Pw to melt the recording layer is in the _{α i T (1 ≦ i ≦} m) of _{time, β i T (1 ≦ i} ≦ Within time m), 0
<Pb ≦ 0.2Pe (However, in β _m T, 0 <
Irradiate recording light with a bias power Pb of (Pb ≦ Pe), m, α _i + β _i−1 (3 ≦ i ≦ m), α ₁ irrespective of the linear velocity
An optical information recording medium for performing recording by making T and α _i T (2 ≦ i ≦ m) constant, and changing β _m so that β _m monotonically increases as the linear velocity decreases. 40. The maximum recording power at each recording linear velocity is P
When w _max, the minimum recording power and Pw _min, recorded by the _{Pw max / Pw min ≦ 1.2,} Pe / Pw = 0.4~0.6, 0 ≦ Pb ≦ 1.5 (mW) 40. The optical information recording medium according to claim 39 for performing: 41. When the recording linear velocity is 5 m / s or less,
41. The optical information recording medium according to claim 40, wherein recording is performed by setting Σα _i <0.5n. 42. When the beta _m at the maximum recording linear velocity beta ^H _m, the beta _m at the minimum recording linear velocity was set to beta ^L _m, the beta _m in other recording linear velocity, the beta ^L _m and beta ^H _m 42. The optical information recording medium according to claim 40, wherein recording is performed by setting Pb and Pe / Pw constant regardless of the recording linear velocity. 43. The optical information recording medium according to claim 39, wherein recording is performed by keeping β _m constant irrespective of the recording linear velocity. 44. At least Pe / Pw ratio, Pb, P
w, α ₁ T, α _i T (2 ≦ i ≦ m), (β ^L _m ,
43. The optical information recording medium according to claim 42, wherein the numerical value of β ^H _m ) is recorded in advance on the substrate by a prepit row or groove deformation. 45. The method according to claim 1, wherein
An optical information recording medium, having a predetermined recording area, wherein the recording area is radially even.
Divided into p zones with width, regardless of radial position
Information is recorded by multiple mark lengths by rotating at a constant angular velocity.
An optical information recording medium for recording, wherein a groove having a predetermined groove meandering signal is formed on a substrate,
The reference cycle of the groove meandering signal changes for each zone, and
(Where q is an integer of 1 ≦ q ≦ p)
Degree <v_q>_ave, Maximum linear velocity <v_q>_max, Minimum line
Speed <v_q> _min, The reference period of the groove meandering signal is Tw_qWhen
Then, <v_q>_aveTw_qIs constant, and_q>_max− <V_q>_min) / (<V_q>
_max+ <V_q>_min) An optical information recording medium satisfying <1%. 46. and 1 zone around the groove, said groove period irrespective of the zone has a meandering constant, when the groove pitch TP, the meander period as Tw _0, approximately ## EQU7 ## The optical information recording medium according to claim 45, wherein a relationship of 2π · TP = a · Tw ₀ · v ₀ (where a is a natural number) is satisfied. 47. The method according to claim 1, wherein
An optical information recording medium, having a predetermined recording area, wherein the recording area is radially even.
Divided into p zones having a width (where p is 20
(Integer greater than 0), rotating at constant angular velocity regardless of radial position
Optical information for recording information with multiple mark lengths
An information recording medium, wherein a groove having a predetermined groove meandering signal is formed on a substrate,
The reference cycle of the groove meandering signal changes for each zone, and
(Where q is an integer of 1 ≦ q ≦ p)
Degree <v_q>_ave, The reference period of the groove meandering signal is Tw_qToss
Then, <v_q> _aveTw_qIs a constant optical information record
Medium. 48. An innermost circumference of the recording area having a radius of 20 to 2
48. The optical information recording medium according to claim 47, wherein the medium is in a range of 5 mm, and the outermost circumference is in a range of 55 to 60 mm in radius. 49. In recording information on the optical information recording medium according to claim 1, an erasing power P capable of crystallizing an amorphous between recording marks.
e, and the time length of one recording mark is nT (T
Is the reference clock cycle, n is an integer of 2 or more), and the time length nT of the recording mark is expressed as follows: η ₁ T, α ₁ T, β ₁ T, α ₂ T, β ₂ T,.
.., Α _i T, β _i T,..., Α _m T, β _m T, η ₂ T (where m is the number of pulse divisions, m = nk, and k is 0 ≦ k)
≤2. Also, Σ _i (α _i + β _i ) + η ₁
+ Η ₂ = n, η ₁ is a real number satisfying η ₁ ≧ 0, η ₂ is η ₂
A real number satisfying ≧ 0, and 0 ≦ η ₁ + η ₂ ≦ 2.0. α
_i (1 ≦ i ≦ m) is a real number satisfying α _i > 0, and β _i (1 ≦ m)
i ≦ m) is a real number satisfying β _i > 0, and Σα _i <0.5n. α ₁ = 0.1 to 1.5, β ₁ = 0.3 to 1.0,
β _m = 0 to 1.5, α _i = 0.1 to 0.8 (2 ≦ i
≦ m). Note that α _i + for i where 3 ≦ i ≦ m.
β _i-1 is in the range of 0.5 to 1.5 and is constant regardless of i. Divided in the order of) irradiated with recording light barrel Pw ≧ Pe becomes recording power Pw to melt the recording layer is in the _{α i T (1 ≦ i ≦} m) of _{time, β i T (1 ≦ i} ≦ Within time m), 0
<Pb ≦ 0.2Pe (However, in β _m T, 0 <
An optical recording method for an optical information recording medium, which comprises irradiating recording light with a bias power Pb that satisfies Pb ≦ Pe). 50. An optical recording method for recording and reproducing data by condensing light having a wavelength of 350 to 680 nm on a recording layer through an objective lens having a numerical aperture NA of 0.55 to 0.9, = N-1 or m = n-2, α ₁ = 0.3 to 1.5, α ₁ ≧ α _i = 0.2 to 0.8 (2 ≦ i ≦ m), α _i + β _i-1 = 50. The optical recording method according to claim 49, wherein 1.0 (3≤i≤m), 0≤Pb≤1.5 (mW), and 0.3≤Pe / Pw≤0.6. 51. A light having a wavelength of 600 to 680 nm passes through an objective lens having a numerical aperture NA of 0.55 to 0.65, is focused on a recording layer via a substrate, and has a minimum mark length of 0.35.
An optical recording method for recording / reproducing data in a range of up to 0.45 μm, wherein n is an integer of 1 to 14, m = n−1, Pb is constant regardless of the linear velocity, and Pe / Pw Can be varied according to the linear velocity in the range of 0.4 to 0.6. (I) In the range of the recording linear velocity of 3 to 4 m / s, the reference clock cycle T is To, and α ₁ = 0 0.3 to 0.8, α ₁ ≧ α _i = 0.2 to 0.4, constant irrespective of i (2 ≦ i ≦ m), α ₂ + β ₁ ≧ 1.0, α _i + β _{i− 1} = 1.0 (3 ≦ i ≦ m), β _m = 0.3 to 1.5, and the recording power P within the time α _i T (1 ≦ i ≦ m)
irradiating the recording light of w _1, (ii) recording linear velocity 6-8 m /
In the range of s, the reference clock cycle T is To / 2, α ′ ₁ = 0.3 to 0.8, α ′ ₁ ≧ α ′ _i = 0.3 to 0.5, and regardless of i Constant (2 ≦ i ≦ m), α ′ _i + β ′ _i−1 = 1.0 (3 ≦ i ≦ m), β ′ _m = 0 to 1.0, α _i T (1 ≦ i ≦ m) Recording power P
when the irradiation with recording light of _{w 2, α 'i> α} i (2 ≦ i ≦ m), and, 0.8 ≦ Pw ₁ /
The optical recording method according to claim 49, wherein Pw ₂ ≦ 1.2. 52. A method for recording information with a plurality of mark lengths by rotating an optical information recording medium having a predetermined recording area at a constant angular velocity, wherein the linear velocity at the innermost circumference of the recording area is 2 to 50. The medium is rotated such that the linear velocity at the outermost periphery of the recording area becomes 4 to 10 m / s, and the recording area comprises a plurality of zones separated by a radius. This is a recording method in which the reference clock period T is changed so that the recording density becomes substantially constant in accordance with the above, wherein m is constant irrespective of the zone, and Pb / Pe and / or α from the outer zone toward the inner zone. 50. The optical recording method according to claim 49, wherein _i (i is at least one of 1? i? m) is monotonously reduced. 53. The recording area is divided into p zones by radius, the innermost side being a first zone, the outermost side being a pth zone, and a qth zone (where q is 1 ≦ q ≦ p). Ω _q , and the average linear velocity is <v _q >
_ave , the maximum linear velocity is <v _q > _max , and the minimum linear velocity is <v _q
> _Min , the reference clock period is T _q , and the time length of the shortest mark is n _min T _q , <v _p > _ave / <v ₁ > _ave is in the range of 1.2 to 3, and <v _q > _max / < _vq > _min is 1.5 or less;
(I) Within the same zone, ω _q , T _q , α _i , β _i , P
e, Pb, and Pw are constant, the physical length of the shortest mark n _min T _q <v _q > _ave is 0.5 μm or less;
T _q <v _q > _ave is substantially constant for all q satisfying 1 ≦ q ≦ p, and m = n−1 or m = n−2, α ₁ = 0.3 to 1.5, α ₁ ≧ α _i = 0.2 to 0.8 (2 ≦ i ≦ m), α _i + β _i−1 = 1.0 (3 ≦ i ≦ m), 0 ≦ Pb ≦ 1.5 (mW), 0.4 ≦ Pe / Pw ≦ 0.6, (ii) Pb, Pw, Pe / P for each zone
w, α _i (1 ≦ i ≦ m), β ₁ , and β _m are variable, and at least α from the outer zone toward the inner zone.
53. The optical recording method according to claim 52, wherein _i (i is at least one of 2≤i≤m) is monotonously reduced. 54. The maximum value of Pw in the recording area is P
When you w _max, the minimum value and Pw _min, Pw _max / Pw
The optical recording method according to claim 53, wherein _min ≦ 1.2. 55. Optical recording for recording and reproducing data by condensing light having a wavelength of 600 to 680 nm through an objective lens having a numerical aperture NA of 0.55 to 0.65 and a recording layer via a substrate. The innermost circumference of the recording area is in a radius of 20 to 25 mm, the outermost circumference is in a radius of 55 to 60 mm, and the average linear velocity of the innermost zone is 3 to 4 m / s. In the q-th zone (where q is an integer of 1 ≦ q ≦ p), the angular velocity is ω _q , the average linear velocity is <v _q > _ave , the maximum linear velocity is <v _q > _max , and the minimum linear velocity is <v. _q > _min , the reference clock period is T _q , and the time length of the shortest mark is n _min T _q
Then, n is an integer of 1 to 14, m = n−1, ω _q , Pb and Pe / Pw are constant regardless of the zone, and T _q <v _q > _ave is 1 ≦ q ≦ It is substantially constant for all q of p, and ## EQU9 ## (< _vq > _max- < _vq > _min ) / (< _vq >
_{max + <v q> min)} < meets 10%, (i) in the first _{^{zone, α 1 1 = 0.3~0.8, α}} 1 1 ≧ α 1 i = 0.2~0.4 constant irrespective of i a is (2 ≦ i ≦ m), α 1 2 + β 1 1 ≧ 1.0, and ^{_{α 1 i + β 1 i-}} 1 = 1.0 (3 ≦ i ≦ m), (ii ) in the first p zone, constant regardless of the alpha ^p ₁ = 0.3 to 0.8, a ^{_{α p 1 ≧ α p i =}} 0.3~0.5 i (2 ≦ i ≦ m), α ^p _i + β ^p _i−1 = 1.0 (2 ≦ i ≦ m), and (ii)
i) In other zones, α ¹ _i ≦ α ^q _i ≦ α
and _{^{p i (2 ≦ i ≦ m}} ), α q 1 is an optical recording method according to any one of claims 52 to 54 to a value between alpha ¹ ₁ and alpha ^p _1. 56. A ^{_{α 1 1 ≧ α q 1 ≧}} α p 1 ( provided that, alpha ¹ ₁
The optical recording method according to claim 55, wherein> α ^p ₁ ). 57. The method according to claim 55, wherein Pb, Pe / Pw, β ₁ and β _m are constant irrespective of the zone, and only α ₁ and α _i (2 ≦ i ≦ m) are changed by the zone. Optical recording method. 58. In recording information on the optical information recording medium according to any one of claims 1, 4, and 7, a recording light having an erasing power Pe capable of crystallizing an amorphous state between recording marks. And irradiates the time length of one recording mark to n
When T is defined as T (T is a reference clock cycle, n is an integer of 2 or more), the time length nT of the recording mark is expressed as follows: η ₁ T, α ₁ T, β ₁ T, α ₂ T, β ₂ T,
..., Α _i T, β _i T,..., Α _m T, β _m T, η ₂ T (where m is the number of pulse divisions, m = nk, and k is 0 ≦ k)
≤2. Also, Σ _i (α _i + β _i ) + η ₁
+ Η ₂ = n, η ₁ is a real number satisfying η ₁ ≧ 0, η ₂ is η ₂
A real number satisfying ≧ 0, and 0 ≦ η ₁ + η ₂ ≦ 2.0. α
_i (1 ≦ i ≦ m) is a real number satisfying α _i > 0, and β _i (1 ≦ m)
i ≦ m) is a real number satisfying β _i > 0. α ₁ = 0.1 ~
1.5, β ₁ = 0.3 to 1.0, β _m = 0 to 1.5, α _i is in the range of 0.1 to 0.8 at 2 ≦ i ≦ m, and It is constant regardless of i. Note that 3 ≦
In the case of i ≦ i, α _i + β _i−1 is in the range of 0.5 to 1.5 and is constant regardless of i. Divided in the order of) irradiated with recording light barrel Pw ≧ Pe becomes recording power Pw to melt the recording layer is in the _{α i T (1 ≦ i ≦} m) of _{time, β i T (1 ≦ i} ≦ Within time m), 0
<Pb ≦ 0.2Pe (However, at β _m T, 0 <
Irradiating recording light with a bias power Pb of Pb ≦ Pe, m, α _i + β _i−1 (3 ≦ i ≦ m), α ₁ irrespective of the linear velocity
An optical recording method wherein T and α _i T (2 ≦ i ≦ m) are fixed, and β _m is changed so that β _m monotonously increases as the linear velocity decreases. 59. The maximum recording power at each recording linear velocity is P
When w _max, the minimum recording power and _{Pw min, Pw max / Pw min} ≦ 1.2, Pe / Pw = 0.4~0.6, claim 58 is 0 ≦ Pb ≦ 1.5 (mW) 2. The optical recording method according to 1. 60. When the recording linear velocity is 5 m / s or less,
The optical recording method according to claim 59, wherein Σα _i <0.5n. 61. When the beta _m at the maximum recording linear velocity beta ^H _m, the beta _m at the minimum recording linear velocity was set to beta ^L _m, the beta _m in other recording linear velocity, the beta ^L _m and beta ^H _m 60. The optical recording method according to claim 59, wherein Pb and Pe / Pw ratio are constant regardless of the recording linear velocity. 62. The optical recording method according to claim 58, wherein β _m is constant irrespective of the recording linear velocity. 63. A method for recording information by a plurality of mark lengths by rotating an optical information recording medium having a predetermined recording area, wherein the recording area is divided into a plurality of zones in a radial direction, and each zone is divided into a plurality of zones. in inner, shall perform recording at a constant linear velocity, the ratio v _out / v _in the recording linear velocity v _{ou t} at the recording linear velocity v _in the outermost zone in the innermost zone is 1.2 to 2
, And the optical recording method according to any one of claims 58 to 62 is changed in accordance with beta _m to the linear velocity of each zone. 64. A method for recording information by a plurality of mark lengths by rotating an optical information recording medium having a predetermined recording area, wherein the recording area is divided into a plurality of zones in a radial direction, and each zone is divided into a plurality of zones. in inner, shall perform recording at a constant linear velocity, the ratio v _out / v _in the recording linear velocity v _{ou t} at the recording linear velocity v _in the outermost zone in the innermost zone is 1.2 to 2
Α _i = 0.3 to 0.6 (2 ≦ i ≦ m) and β _m = 0 to
1.5, m, α _i + β _i-1 (3 ≦ i ≦ m), α ₁ irrespective of the linear velocity
T, Pe / Pw, and Pb to be constant, an optical recording method according to claim 49 for changing the alpha _i and / or beta _m according to the linear velocity. Upon performing recording of information to 65. An optical information recording medium according to any one of claims 45 to 48, the reference clock period T _q is the reference period Tw _q of the groove meandering in each zone An optical recording method characterized by being generated as a multiple or a divisor.