JP3485040B2 - Optical information recording medium and optical recording method - Google Patents

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 having a phase-change recording layer such as D for high-density recording and an optical recording method, and in particular, linear velocity dependence and recording power dependence at the time of one-beam overwrite, and temporal stability of recording marks. To an improved optical recording medium and optical recording method.

[0002]

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

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

Since the phase-change recording medium can perform the erasing and re-recording processes only by intensity modulation of one focused light beam, recording and recording in the phase-change recording medium such as a CD-RW and a rewritable DVD. Includes overwrite recording in which recording and erasing are performed simultaneously. For recording information using phase change, crystalline, amorphous, or a mixed state thereof can be used, and a plurality of crystalline phases can be used, but the rewritable phase-change type currently in practical use A recording medium is generally recorded by forming a non-recorded / erased state into a crystalline state and forming an amorphous mark. A chalcogen element, that is, a chalcogenide alloy containing S, Se, and Te is often used as the material of the recording layer.

For example, a GeSbTe system containing GeTe-Sb ₂ Te ₃ pseudo binary alloy as a main component, InTe-Sb ₂
In ₃ SbTe based on Te ₃ pseudo binary alloy, S
AgInSbT the b _{0. 7} Te _0.3 whose main component is a eutectic system
Examples include e-based alloys and GeSnTe-based alloys. 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
Compositions in the vicinity of intermetallic compounds such as ₂ Te ₅ have been mainly put into practical use.

These compositions are characterized by crystallization without phase separation, which is peculiar to intermetallic compounds, and have a high crystal growth rate. Therefore, initialization is easy and recrystallization rate during erasing is fast. Therefore, conventionally, as a recording layer exhibiting practical overwrite characteristics, a pseudo binary alloy system or a composition in the vicinity of an intermetallic compound has been noted (reference Jpn.J.Appl.Phys., Vol.69 (199
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 grain boundaries and irregular sizes, and optical anisotropy is remarkable depending on their orientations, so that optical white noise is likely to occur. Further, such crystal grains having different grain sizes and optical characteristics are likely to grow around the amorphous mark, so that the jitter of the mark is likely to increase, or because the optical characteristics are different from those of the surrounding crystals, It was easy to detect it as the rest. Therefore, there is a problem in that good reproduction characteristics cannot be obtained in recording at a high linear velocity or high-density mark length modulation recording. Specifically, the shortest mark length is 0.6 μm in the rewritable DVD standard, but it has been found that the jitter is sharply increased as the shortest mark length is further shortened.

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

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 light absorption in the amorphous state is taken away by this absorption layer. For example, an absorption 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), pp2516-2520).

However, such a layer structure has a problem in heat resistance and adhesiveness of the absorption layer, and repetitive overwriting causes remarkable deterioration such as microscopic deformation and peeling. Further, peeling or the like is likely to occur, so that stability with time is also impaired. 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 2} Te ₃ pseudo binary alloy recording layer, the birefringence has a wavelength dependence that the real part becomes smaller and the imaginary part becomes larger as the wavelength becomes shorter. It is difficult to achieve the condition 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 erasing ratio as high as 40 dB can be obtained. With the conventional 4-layer structure, high linear velocity and high-density mark length modulation recording can be performed without correction of absorptance. . However, since high-speed recording usually means that the crystallization speed is high and erasing is easy, amorphous marks are also easily crystallized, and the recorded marks often have poor stability over time.

[0012]

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

However, conventionally, high-speed recording and mark stability are considered to be contradictory properties, and it has been considered difficult to satisfy both of them at the same time. As a result of repeated research on the principles of crystallization and amorphization, the present inventors 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 capable of excellently recording a short mark at high speed and having good mark stability, and an optical recording method suitable for the same.

[0014]

The first gist of the present invention is as follows.
First protection on the substrate in order from the incident direction of recording / reproducing light
Layer, phase-change recording layer, second protective layer, reflective layer.
The crystalline part of the recording layer to an unrecorded / erased state, and an amorphous part
Is set to the recording state, and the shortest mark length is 0.5 μm or less.
Optical information recording for recording information by recording mark length
It is a recording medium, and the film thickness of the phase change recording layer is 5 nm or more.
Below 25 nm, in the GeSbTe ternary phase diagram,
Straight line A connecting (Sb _0.7 Te _0.3 ) and Ge, (Ge _0.03 S
b _0.68 Te _0.29 ) and (Sb _0.95 Ge _0.05 )
B, directly connecting (Sb _0.9 Ge _0.1 ) and (Te _0.9 Ge _0.1 ).
Line C and straight line D connecting (Sb _0.8 Te _0.2 ) and Ge 4
The area enclosed by the straight lines of the book (but not including the boundary
Thin film containing GeSbTe alloy as the main component
The second protective layer has a film thickness of 5 nm or more and 30 nm or less.
Present in an optical information recording medium characterized by being below
It

[0015]

Another aspect of the present invention is to use in combination with the above medium.
A further preferable optical recording method exists.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the phase change medium in which the crystalline state of the recording layer is the unrecorded / erased state and the amorphous state is the recorded state, the erasure is performed as an amorphous portion or a melted portion. It has been found that a medium, which is recrystallized substantially by the crystal growth from the boundary with the peripheral crystal part, can perform stable recording at high speed and high density. 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 stability over time.

Generally, the erasing of the amorphous mark is performed by heating the recording layer to a temperature above the crystallization temperature and below the melting point to bring it into an amorphous solid phase state or a molten state, and then recrystallizing it when cooled. Occur. According to the research conducted by the present inventors, erasure of amorphous marks, that is, recrystallization, is (1) formation of crystal nuclei in an amorphous region, and (2) formation of an amorphous part or a fused part, The process proceeds by two processes of crystal growth starting from the boundary with the part, but by making the former crystal nucleation hardly occur and substantially utilizing only the latter crystal growth process, It turned out that such an effect can be obtained.

Usually, crystallization proceeds above the crystallization temperature and below the melting point but below the melting point, crystal nucleation proceeds on a relatively low temperature side and crystal growth proceeds on a high temperature side. It is not that erasing cannot be performed without crystal nucleation, and erasing is possible if crystal growth proceeds at high speed with the boundary point with the peripheral crystal region surrounding the amorphous part or the melted part as nuclei. In particular, a finer mark or a shorter mark is likely to be instantly crystallized to the center of the mark only by such crystal growth from the peripheral crystal part, so that the mark can be completely erased in an extremely short time. Therefore, in a high-density recording medium that uses minute marks with a shortest mark length of 0.5 μm or less,
The effect is remarkable, erasing can be performed in the order of 100 nanoseconds or less, and high-speed overwriting is possible. Generally, the shorter the shortest mark length is, the higher the density of recording is possible, but from the viewpoint of the stability of the mark, 10 nm or more is preferable.

Further, the narrower the width of the mark is, the easier it is to crystallize instantly to the center of the mark only by the crystal growth from the peripheral crystal part, which is preferable. Therefore, it is preferable to set the track pitch of the information recording track to, for example, 0.8 μm or less so that the mark does not spread laterally. Normally, the mark width is about half the track pitch. Generally, the narrower the track pitch, the higher the recording density, but from the standpoint of mark stability, the track pitch is 0.1 μm.
m or more is preferable. The tracks may be only grooves or both grooves and lands.

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

Particularly, in a normal use range of less than 100 ° C., the recorded amorphous mark is extremely stable and the amplitude of the recorded signal is hardly deteriorated. On the contrary, it can be concluded from such stability over time that there is almost no crystal nucleation. Further, the medium of the present invention has an advantage that a smooth mark edge with extremely little fluctuation can be formed in mark length recording. Generally, when recording an amorphous mark, the recording layer is once melted and re-solidified to be amorphous, but since the edge portion of the mark has a lower temperature than the center,
Conventionally, recrystallization due to the growth of crystal nuclei is likely to occur at the edge portion of the mark, and coarse grains in which amorphous is mixed are generated,
It was a cause of mark edge fluctuation.

In the medium of the present invention, the crystal growth from the boundary between the amorphous part or the melted part and the crystal part is dominant at the time of erasing, and the speed is high, which means that the same principle also works at the time of recording. Even when the molten region is re-solidified and becomes amorphous, only the crystal growth from the peripheral crystal part occurs, crystallization due to the growth of crystal nuclei does not easily occur, and the mark edge does not easily fluctuate. That is, since the crystal growth from the peripheral crystal part progresses only in the relatively high temperature region close to the melting point even if it is above the crystallization temperature and below the melting point vicinity and hardly progresses at the low temperature, at the time of resolidification from the molten state, Of the amorphous mark, the boundary shape of the amorphous mark is determined only by the cooling rate at the time when the temperature decreases and passes the melting point.

Further, coarse grains in which amorphous particles are mixed due to crystal nucleus growth that occurs during re-solidification, which has been a conventional problem, are hardly formed around the amorphous marks. This has been found to be extremely effective in suppressing noise due to fluctuations in the mark edge. Furthermore, the mark edge shape is stable and does not change over time,
Not only is the initial jitter small, but there is almost no deterioration 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 part serves as a nucleus for crystal growth, so that a crystal nucleus is hardly 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 by a transmission electron microscope. When both recording layers after the formation of the amorphous marks are directly irradiated with erasing light of relatively low power, GeTe-Sb ₂
In the Te ₃ -based recording layer, crystallization is observed to progress from the central portion of the amorphous mark where the temperature rises, whereas in the recording layer of the present invention, crystals grow 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 which is erased on the basis of such a principle is a composition near the Sb _0.7 Te _0.3 eutectic point and an excess of Sb.
And it is often found in alloy systems containing other elements up to about 20 atomic%. That is, 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 the above) is a thin film containing an alloy as a main component. In the alloy containing Sb _0.7 Te _0.3 with an excess of Sb, the crystal growth from the crystal in the peripheral portion of the amorphous mark is GeTe-S.
b ₂ Te ₃ because it is significantly larger than the pseudo binary alloy system,
It has the feature of being able to overwrite at high linear velocity.
Excess Sb does not promote random crystal nucleus generation and crystal nucleus growth in the amorphous mark, but significantly increases the crystal growth rate from the peripheral crystal part. However, in the SbTe binary alloy, crystal nucleation also occurs to some extent, so that the stability of the amorphous mark with time is extremely poor, and it is necessary to add an appropriate element.

According to the studies by the present inventors, the addition of Ge is extremely effective in suppressing the formation of crystal nuclei. Now, whether or not 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 stability over time. As a specific evaluation method, when performing an accelerated environmental test under high temperature and high humidity,
A method of measuring the modulation degree of the reproduction signal can be mentioned.

That is, when a signal is recorded with a plurality of mark lengths of the shortest mark length of 0.5 μm or less, the degree of modulation of the signal reproduced immediately after recording is set to M _0, and after recording, 80 ° C. 80
If the modulation degree of the signal reproduced after 1000 hours has passed under the condition of% RH is M ₁ ,

[0029]

[Formula 11] M ₁ / M ₀ ≧ 0.9

It is 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
erted) modulation or the like can be used, but a random signal as shown in FIG. 6 is recorded with the shortest mark length of 0.5 μm or less. In this evaluation, the shortest mark length is 0.
It is preferably about 2 μm or more. Note that it is not necessary to satisfy the above formula under all the evaluation conditions, and the above formula may be satisfied under one evaluation condition.

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

In the recording layer of the present invention, crystal growth from the peripheral crystal portion is likely to occur in a high temperature region just below the melting point, so that even when the recording layer is melted and re-solidified to form an amorphous mark, the peripheral crystal portion is formed. 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 melting region is recrystallized almost instantly.

This can be confirmed by the following experiment. Record
0.6mm thick polycarbonate with grooves for guiding reproduction light
On the gate substrate (ZnS)₈₀(SiO₂)₂₀First protection
Layer thickness 68nm, Ge_0.05Sb_0.71Te _0.24Recording layer
Film thickness 18 nm, (ZnS)₈₀(SiO₂)₂₀Second protective layer
With a film thickness of 20 nm, Al_0.995Ta_0.005Reflective layer thickness 2
50 nm, provided in this order, and an ultraviolet curable resin protective layer
To a film thickness of 4 μm. Put these two on the side with the recording layer
The inside is laminated with a hot melt adhesive to make an optical recording medium.
did. This recording layer composition is over at a linear velocity of about 7 m / s or more.
Sb / Te≈3 is set so that writing is possible. In this medium,
Elliptical laser light with major axis of about 100 μm and minor axis of about 1.5 μm
Was initialized by melt recrystallization by scanning in the short axis direction.

This medium has a wavelength of 637 nm and NA = 0.6.
The focused light of No. 3 was irradiated along the guide groove at a linear velocity of 7 m / s. After the recording light having a recording power Pw of 10 mW was applied as a direct current, the power was drastically reduced to 1 mW. That is,
The recording light was substantially cut off. The beam diameter is about 0.9.
In μm, the Gaussian beam corresponds to a region where the energy intensity is 1 / e ² or more of the peak intensity.

FIG. 2 shows changes in reflectance before and after the recording light is blocked. As shown in the lower part of FIG. 2, the recording light was cut off as time passed. The recording light is continuously irradiated on the left side of the lower part of FIG. 2, that is, in the form of direct current, and is blocked on the right side. When the same region 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 the change in reflectance.

The reflectance decreases near the moment when the recording light is interrupted, and before and after that, the reflectance is almost the same.
By TEM observation, it was confirmed that the reflectance-reduced portion was amorphous and that it was crystalline before and after that. 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 necessary for the amorphous formation cannot be obtained. Thus, by cutting off the recording light once, it is possible to cut off the residual heat from the subsequent portion and increase the cooling rate. Incidentally, when the recording power Pw was set to 7 mW or more, the amorphous mark was formed due to the interruption of the recording light.

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

In the present invention, recrystallization during resolidification of the melted portion almost always occurs only by crystal growth from the surrounding solid phase crystal portion. Therefore, since the recrystallized portion is not formed in the central portion of the amorphous mark, a smooth and continuous mark edge is formed. Conventionally, it has been considered that such a material that is recrystallized extremely easily is not suitable for a recording layer for recording a mark length. This is because if the recording light is irradiated for a long time to form a long mark, most of the melted region will be crystallized.

However, according to the study by the present inventors, in the high density recording with the shortest mark length of less than 0.5 μm,
A better jitter can be obtained by positively using the competitive process of the amorphization of the molten region and the recrystallization from the boundary of the solid phase crystal part in the periphery. Therefore, as described later, 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 in forming a mark of a length nT.

When the recording is performed by the pulse division method, as shown in FIG. 1, arrow-shaped (or crescent-shaped) amorphous portions are connected to form an amorphous mark. The shape of the leading end of the mark is determined only by the shape of the leading end of the leading arrow-shaped amorphous portion, and the shape of the trailing end of the mark is determined only by the shape of the trailing end of the trailing arrow-shaped amorphous portion. Usually, since the starting shape of the amorphous portion is smooth, the starting shape of the mark is also smooth. This is because the cooling rate is kept sufficiently high due to the escape of heat to the front, so that it substantially reflects the shape of the tip of the melted region and is therefore dominated by the rise time of the recording pulse. 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 trailing edge of the amorphous portion is determined by the cooling rate determined by the fall time of the recording pulse and the size of the recrystallized region that advances from the periphery, particularly the trailing edge crystalline portion. In order to make the cooling rate sufficiently high, the fall of the Pw application section is preferably 2-3 nanoseconds or less. The size of the recrystallized region can be accurately controlled by the length of the off pulse, that is, the Pb application section. Furthermore, by applying the above-mentioned rapid cooling structure as the 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 steep near the trailing edge of the mark so that the mark edge position is It is also important that there is no fluctuation

The inventors of the present invention have made earnest studies on an optical recording medium capable of recording short marks at high speed and having excellent stability of the recording marks. As a result, Ge is added in the vicinity of the Sb _0.7 Te _0.3 eutectic composition. It was found that the specified composition was particularly excellent, and an optical recording medium excellent in other characteristics was obtained by appropriately selecting the layer structure. That is, Sb _0.7 Te
Focusing on a non-conventional ternary alloy in which excess Sb and Ge are added to _0.3 , 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 and using a recording layer composition with a very limited Ge-Sb-Te ratio was It has been found that, in high-density mark length modulation recording, repeated overwrite durability and stability over time are particularly excellent.

That is, in the GeSbTe ternary phase diagram, a straight line A connecting (Sb _0.7 Te _0.3 ) and Ge (Ge
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 ).
A thin film containing GeSbTe alloy as a main component having a composition of a region surrounded by four straight lines C connecting (Sb _0.8 Te _0.2 ) and (Sb _0.8 Te _0.2 ), and Ge (not including the boundary line). The recording layer. By using the layer structure described later for this recording layer, the medium becomes very suitable for high density mark length modulation recording with a shortest mark length of 0.5 μm or less. Then, it is possible to obtain the same recording density as DVD and excellent reproduction compatibility with DVD.

In addition, repeated overwrite durability,
It is possible to secure a wide margin for obtaining good jitter with respect to variations in recording power and erasing power. Within this composition range, in the Sb _y Te _1-y alloy, the larger the Sb amount is from y = 0.7, the more the Sb amount increases, and the crystallization speed is high and overwriting at a high linear velocity is possible.

More specifically, in EFM plus modulation recording (mark length modulation recording of 8-16 modulation), the length of the shortest 3T mark is 0.4 μm or 0.
Even if it is shortened to about 35 μm, good jitter can be obtained. Further, a sufficient servo signal can be obtained, and tracking servo can be applied by the existing read-only DVD drive. Further, overwriting is possible at any linear velocity 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 excessive Sb amount is controlled, the above-described high quality and high density overwriting is possible at a high linear velocity of 8 m / s or more. Further, by changing the recording pulse division method (pulse strategy) according to the linear velocity as described later, good overwriting becomes possible in a wide linear velocity range including at least 3 to 8 m / s.

The composition will be described in detail below.
In the composition near the Sb _0.7 Te _0.3 eutectic point in which 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
When there is no Sb in excess of _{0.3, the} erasing performance is insufficient and it is practically impossible to overwrite. Further, since there is almost no nucleation at the time of initialization, there is a problem that the initialization is difficult and the productivity is very poor (line A).

On the other hand, Sb _0.7 Te _0.3 eutectic binary alloy with S
When the amount of b is increased, the crystallization speed is increased, but at the same time, the crystallization temperature is decreased, and the temporal stability of the amorphous mark is impaired. Further, it is not suitable for recording at a low linear velocity of around 3 m / s, and the formed amorphous mark disappears by irradiation with reproducing light (laser power of about 1 mW) for a short time. Therefore, the straight line D connecting (Sb _0.8 Te _0.2 ) and Ge
No excess of Sb should be included.

In addition, the excess Sb defined by the straight lines A and D
In the range of the amount, if the SbTe binary is left as it is, the crystallization temperature is low and the crystal nuclei of the excess Sb are present, so that the amorphous mark becomes too unstable. To do. The four-coordinate bond of Ge almost completely suppresses crystal nucleation. As a result, the crystallization temperature rises and the stability over time increases. (Ge _0.03 Sb _0.68 Te _0.29 )
The straight line B connecting (Sb _0.95 Ge _0.05 ) and (Sb _0.95 Ge _0.05 ) defines this condition. More preferably, (Ge _0.03 Sb _0.68 Te
Ge is contained more than the straight line B'connecting _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 is deteriorated, and the repetitive overwriting causes a Ge compound having a high melting point, particularly Ge.
Te tends to segregate. Further, crystallization of the amorphous film immediately after film formation becomes extremely difficult, which is not preferable (straight line C). In order to reduce the jitter, Ge is more preferably 7.5 atomic% or less.

When the linear velocity is 3 m / s or more, the overlay
The recording layer to Ge_x(Sb _yTe_1-y)_1-xCombined
A thin film containing gold as a main component (0.04 ≦ x <0.10, 0.
72 ≦ y <0.8) is preferable. Ie the line
For recording at a speed of 3 m / s or more, increase the Sb amount
_yTe_1-yIn alloy, it is preferable that y ≧ 0.72
Yes. However, by increasing the amount of Sb, the amorphous mark
The stability of x..0.
It is preferable to add a large amount of 04 and Ge. Furthermore, the linear velocity
To overwrite at a speed of 7 m / s or more, set the recording layer to G
e_x(Sb_yTe_1-y)_1-xAlloy-based thin film
(0.045 ≦ x ≦ 0.075, 0.74 ≦ y <0.
8) is preferred. That is, a linear velocity of 7 m / s or more
In the above record, the Sb amount was increased to_yTe
_1-yIt is preferable that y ≧ 0.74 in the alloy. This
At this time, the Ge amount is increased in order to improve the stability of the amorphous mark.
x ≧ 0.045. On the other hand, jitter is worse at high linear velocity
The amount of Ge is x ≦ 0.07 to compensate for this.
Set to 5.

Heretofore, reports have been made on the ternary composition of GeSbTe, or the composition of the recording layer containing the additive element with the ternary composition as the matrix (Japanese Patent Laid-Open No. 61-2).
58787, 62-53886, and 62.
-152786, JP-A-1-63195,
1-211249 and 1-277338). However, all of the compositions described in these figures are Sb from the straight line A connecting (Sb _0.7 Te _0.3 ) and Ge.
Poor composition, which is different from the composition range of the present invention. Rather, they are mainly composed of Sb ₂ Te ₃ metal compound composition. Further, in the GeTe-Sb ₂ Te ₃ pseudo binary alloy system, contrary to the present invention, when excessive Sb has the effect of delaying the crystallization speed, when overwriting at a high linear velocity of 5 m / s or more, It is rather detrimental to include an excess of Sb in the GeTe—Sb ₂ Te ₃ line, especially in the Ge ₂ Sb ₂ Te ₅ composition. 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 Japanese Patent Application Laid-Open No. 1-1100475 (FIG. 4).
(A) Composition range α) and those disclosed in JP-A-1-303643 (FIG. 4 (a) Composition range β).

However, Japanese Patent Application Laid-Open No. 1-1100475 discloses that Sb _1-x Te _x , which is the matrix composition, is 0.1.
Very wide range of 0 ≦ x ≦ 0.80, Sb _0.7 Te
_The idea of the present application that the repeated overwrite durability and the temporal stability are excellent in high-density recording is not found by utilizing only the area where Sb is _more than _0.3 . Japanese Patent Laid-Open No. 1-30
Japanese Patent No. 3643 discloses S for high density recording as in the present application.
There is no mention of the adverse effect that the aged stability of the amorphous mark is impaired when b is excessively contained beyond the straight line D. Further, none of the publications mentions the adverse effect of excessive inclusion of Ge beyond the straight line C.

Further, as a composition which partially overlaps with the composition of the recording layer of the present invention, as shown in FIG.
-115685 gazette (composition range (gamma)), the same 1-2513.
No. 42 (composition range δ), No. 3-71887 (composition range ε) and No. 4-28587 (composition range η). JP-A-1-115685
In the publication, Au and Pd are added with the composition range γ as the base material, but for the purpose of low density recording, the composition of the present invention is substantially distinguished by the straight line A and the 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 4 m / s, frequency 1.75 MHz, square wave of duty 50%) 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 short marks.

The composition range δ disclosed in Japanese Patent Laid-Open No. 1-251342 is based on an Sb _0.7 Te _0.3 eutectic system containing about 10 atomic% or more of Ge, and is extremely Ge-rich GeSb.
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 in which Ge is contained in an amount of more than 10 atomic%, the crystallization rate is slow as described above, and the initialization operation for crystallizing the recording layer after film formation is particularly difficult, and therefore productivity is high. There is a serious problem that it is low and cannot be put to practical use. In this publication, Au and Pd, which are crystal nuclei, are separately added in order to overcome the problem of the crystallization rate. However, in the region where Ge is smaller than that of the straight line C as in the present invention, such a requirement is required. There is no. Further, in this publication, it is described that when the amount of Ge is less than 10 atom%, a sufficient change in light amount cannot be obtained in the recording portion and the non-recording portion. By devising the layer structure including the above, a very large change in the reflected light amount with a modulation degree of 60% or more is obtained. JP-A-3-71
The composition range ε of the 887 publication is intended for low density recording,
It is substantially distinguished from the composition according to the invention by the straight line C. In particular, by utilizing the composition range of the present invention, the idea of the present application that the repeated overwrite durability and the temporal stability are excellent in high density recording is not found. JP-A-4-2858
The composition range η in Japanese Patent No. 7 is extremely Sb rich and Ge.
It contains a rich composition and is substantially distinguished from the composition of the invention by a straight line D. As described above, none of the above publications has disclosed the technical problem regarding the high-density mark length modulation recording for which the shortest mark length is 0.5 μm or less, which is the object of the present invention. There is no disclosure about selection of the optimum composition for that purpose and improvement of the layer structure and 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 combines at least 3 m / s to 8 m / s at the time of high density mark length modulation recording with a shortest mark length of 0.5 μm or less by combining the recording layer having the above composition with the following layer constitution. It is possible to realize a medium that can be overwritten in a wide linear velocity range that preferably covers 1 m / s to 10 m / s. Then, it is possible to maintain reproduction compatibility with a so-called DVD. At least one of the upper and lower sides of the phase-change recording layer is covered with a protective layer.

Further, as shown in FIG. 5A, the substrate 1 /
It has a structure of a first protective layer 2, a recording layer 3, a second protective layer 4 and a reflective layer 5, and is covered with an ultraviolet ray or thermosetting resin (protective coat layer 6). The order of the layers as shown in FIG. 5A is suitable for irradiating the recording layer with a focused light beam for recording and reproduction through the transparent substrate. Alternatively,
By reversing the order of the above layers, the substrate 1 / reflection layer 5 / second protective layer 4 / recording layer 3 / first protective layer 2 are reversed as shown in FIG.
It is also possible to adopt a configuration in which the layers are stacked in this order. This layer structure is
It is suitable when the 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 highly necessary to reduce the distance between the recording layer and the objective lens.

With the structure shown in FIG. 5A, a transparent resin such as polycarbonate, acryl, or polyolefin, or transparent glass can be used for the substrate. Among them, the polycarbonate resin is the most preferable because it has a track record of being most widely used in CD and is inexpensive. Similarly, resin or glass can be used in the configuration shown in FIG. 5B, but the substrate itself does not need to be transparent, and it is preferable to use glass or aluminum alloy in order to enhance flatness and rigidity. is there.
A groove having a pitch of 0.8 μm or less for guiding the recording / reproducing light is provided on the substrate, but the groove does not necessarily have to be a trapezoidal shape geometrically. 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 surface of the substrate and the second protective layer 4 is provided on the recording layer 3 in order to prevent deformation due to high temperature during recording. It is provided. The second protective layer 4 also has a function of preventing mutual diffusion of the recording layer 3 and the reflective layer 5, suppressing deformation of the recording layer, and efficiently releasing heat to the reflective layer 5. Also in FIG. 5B, the second protective layer 4 is the recording layer 3 when viewed from the incident side of the focused light beam.
It has a function of preventing mutual diffusion between the reflective layer 5 and the reflective layer 5, heat dissipation, and preventing deformation of the recording layer. The first protective layer in FIG. 5B is
It has functions of preventing deformation of the recording layer, preventing direct contact between the recording layer and air (preventing oxidative 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. 5 (b),
It is desirable to provide a harder dielectric or amorphous carbon protective film or an ultraviolet ray or thermosetting resin layer further outside the first protective layer 2. Alternatively, it is also possible to bond a transparent thin plate having a thickness of about 0.05 to 0.6 mm and allow the focused light beam to enter through this thin plate.

Further, in a medium such as a DVD,
The medium of FIG. 5A has a structure in which the recording layer surface is placed inside and the medium is bonded with an adhesive. On the other hand, in the medium of FIG. 5B, the recording layer surface is the outer side, and the recording medium is bonded. Furthermore, FIG.
In the medium of (b), tracking grooves may be formed on both surfaces of a single substrate by injection molding, and a multilayer film may be formed on both surfaces by a sputtering method. The recording layer 3, the protective layers 2 and 4, and the reflective layer 5 are formed by a sputtering method or the like. It is desirable to form a film by an in-line apparatus in which the target for recording layer, the target for protective layer, and the target for reflective layer material, if necessary, are installed in the same vacuum chamber in order to prevent oxidation and contamination between the 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 and Ca of metals and semiconductors that have high transparency and high melting point,
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 or mix them for controlling the refractive index and the like. is there.

The composition ratio or 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 film has a required property
The materials, composition ratios, and mixing ratios can be made different. Considering the repetitive recording characteristics, the film density of these protective layers is preferably 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 formula 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 sufficient contrast, and the crystallization speed tends to be slow, which makes it difficult to erase in a short time.
On the other hand, when the thickness exceeds 100 nm, it becomes difficult to obtain optical contrast and cracks easily occur. Further, it is necessary to obtain a contrast enough to be compatible with a read-only disc such as a DVD, and 5 nm for high-density recording in which the shortest mark length is 0.5 μm or less.
It is preferably 25 nm or less. If the thickness is less than 5 nm, the reflectance becomes too low, and the effects of a non-uniform composition and a sparse film at the beginning of film growth are likely to occur, which is not preferable.

On the other hand, if it is thicker 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 are disturbed and the jitter tends to be high. Furthermore, the volume change due to the phase change of the recording layer becomes remarkable, and the repeated overwrite durability deteriorates, which is not preferable. From the viewpoints of mark edge jitter and repeated overwrite durability, the thickness is more preferably 20 nm or less. The density of the recording layer is preferably 80% or more of the bulk density, more preferably 90% or more.
The bulk density referred to here can, of course, be measured by making an alloy lump, but in the above formula (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 sputtering film formation method, the density of the recording layer is set by reducing the pressure of the sputtering gas (rare gas such as Ar) at the time of film formation, or by arranging the substrate close to the front surface of the target. It is necessary to increase the amount of high energy Ar applied to the layer. High-energy Ar means that Ar ions irradiated on the target for sputtering are partially repelled and reach the substrate side, or Ar in plasma is used.
Either of the ions is accelerated by the sheath voltage over the entire surface of the substrate and reaches the substrate. The irradiation effect of such a high-energy rare gas is called the atomic peening effect. In sputtering with Ar gas that is generally used, Ar is mixed in the sputtered film due to the atomic peening effect. Depending on the amount of Ar in the film, atomi
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 likely to be formed. On the other hand, if the amount of Ar is large, the irradiation of high energy Ar is intense and the density is high, but
When r is repeatedly overwritten, it becomes a void and precipitates, deteriorating the durability of repetition. A suitable amount of Ar in the recording layer film is 0.1 atom% or more and 1.5 atom% or less. Furthermore, it is preferable to use high-frequency sputtering rather than direct-current sputtering because the amount of Ar in the film can be reduced and a high-density film can be obtained.

In the present invention, the recording layer is composed of a thin film whose main component is the GeSbTe alloy having the above composition. That is, it suffices that the ratio of the amount of each element of Ge, Sb, and Te in the recording layer is within the above composition range, and if necessary, other elements may be added 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 atom% or more and 5 atom% or less. However, the addition of more than 5 atomic% is not preferable because it lowers the crystallization rate and deteriorates the erasing performance.

In order to increase the stability with time without decreasing the crystallization rate 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,
Add 0.1 atom% or more and 5 atom% or less. The total addition amount of these additional elements and Ge to SbTe is 1 in total.
It is preferably 5 atomic% or less. If it is contained excessively, phase separation other than Sb will be induced. In particular, when the Ge content is 3 atomic% or more and 5 atomic% or less, the addition effect is large. To improve stability over time and finely adjust the refractive index, S
It is preferable to add at least one of i, Sn, and Pb in an amount of 5 atomic% or less. The total content of these additional elements and Ge is preferably 15 atomic% or less. These elements are Ge
It has the same 4-coordination network as.

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

By the way, the recording layer 3 of the recording medium of the present invention is usually amorphous after the film formation. Therefore, after film formation,
It is necessary to crystallize the entire surface of the recording layer to be in an initialized state (unrecorded state). As the initialization method, Sb _0.7
An alloy containing Te _0.3 with an excess of Sb can be initialized by annealing in the solid phase. However, with a composition containing Ge, the recording layer is melted once and gradually cooled during re-solidification to melt. Initialization by recrystallization is desirable. This recording layer has almost no nuclei for crystal growth immediately after film formation, and it is difficult to crystallize in the solid phase. However, it seems that recrystallization proceeds at a high speed mainly by crystal growth.

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

After that, the erasing power Pe is written on the same track.
If the reflectance in the erased state obtained by irradiating the erasing light of (≦ Pw) in a direct current is almost the same as the reflectance in the unrecorded initial state, the initialized state is confirmed to be a crystalline state during melting. it can. This is because the recording layer is once melted by the irradiation of the recording light, and the state of being completely recrystallized by the irradiation of the erasing light undergoes the process of melting by the recording light and recrystallization by the erasing light. This is because it is in a simplified state. Note that the reflectance in the initialized state R _ini and the reflectance in the molten recrystallized state R _cry are almost the same as (R _ini −R
It is said that the difference in reflectance between the two defined by _cry ) / {(R _ini + R _cry ) / 2} is 20% or less. Usually, the reflectance difference is larger than 20% only by solid phase crystallization such as annealing.

Next, layers other than the recording layer will be described. The layer structure of the present invention belongs to a type of layer structure called a quench structure. The rapid cooling structure adopts a layer structure that promotes heat dissipation and increases the cooling rate during resolidification of the recording layer, thus avoiding the problem of recrystallization during the formation of amorphous marks and achieving high temperature crystallization. Achieve an erase 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 apt to be destroyed by deformation when melted, and the heat dissipation effect is too large, and the power required for recording unnecessarily increases.

The film thickness of the second protective layer of the present invention has a great influence on the durability in repeated overwriting, and is particularly important for suppressing the deterioration of jitter. Film thickness is 30 nm
In the case of thicker recording, the recording side of the second protective layer,
The temperature difference between the reflective layer side and the reflective layer side becomes large, and the protective layer itself tends to be asymmetrically deformed due to the difference in thermal expansion between both sides of the protective layer. Repeating this is not preferable because it causes microscopic plastic deformation to accumulate inside the protective layer, resulting in increased noise. When the recording layer of the present invention is used, low jitter can be realized in high density recording with a shortest mark length of 0.5 μm or less. However, according to the study by the present inventors, a laser with a short wavelength is used to realize high density recording. When a diode (for example, a wavelength of 700 nm or less) is used, further attention needs to be paid to the layer structure of the quenching structure. In particular, in studying the one-beam overwrite characteristic 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 is effective in achieving a high erasing ratio and erasing. It was found to be important for widening the power margin.

This tendency is due to wavelengths of 630 to 680 nm and 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 a low thermal conductivity is particularly used as the second protective layer. The film thickness is preferably 10 nm or more and 25 nm or less. In either case,
The erasing ratio and erasing power margin can be improved by forming the reflective layer 5 provided thereon with a material having particularly high thermal conductivity. According to the study, in 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 structure that can flatten not only the temperature distribution in the film thickness direction and time change but also the temperature distribution in the film surface direction (direction perpendicular to the recording beam scanning direction) as much as possible.

By properly designing the layer structure of the medium, the inventors of the present invention flatten the temperature distribution in the cross-track direction in the medium so that the medium is not melted and re-amorphized. We tried to widen the width that can be recrystallized and widen the erase ratio and erase power margin. On the other hand, it was found that the temperature distribution in the recording layer becomes flat by promoting heat dissipation from the recording layer to the reflective layer having extremely high thermal conductivity through the second protective layer having a low thermal conductivity and a very thin thickness. . Even if the thermal conductivity of the second protective layer is increased, the heat dissipation effect is promoted, but if the heat dissipation is promoted too much, the irradiation power required for recording will increase, that is, the recording sensitivity will decrease significantly.

In the present invention, a thin second film having a low thermal conductivity is used.
It is preferable to use a protective layer. Thin second with low thermal conductivity
By using the protective layer, heat conduction from the recording layer to the reflective layer may be delayed in time from several nsec to several tens of nsec at the start of irradiation of the recording power, and thereafter heat dissipation to the reflective layer may be promoted. Therefore, the recording sensitivity is not unnecessarily lowered due to the heat radiation. Conventionally known SiO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , AlN, Si
The protective layer material containing N or the like as a main component is not preferable as the second protective layer 4 of the medium of the present invention because its thermal conductivity is too high. As described above, the thermal conductivity of metal oxides and nitrides is higher than that of the following protective layer used in the protective layer of the present invention by one digit or more, 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, heat conduction in the film thickness direction becomes more remarkable than in the film surface direction of the recording layer, and the effect of improving the temperature distribution in the film surface direction cannot be obtained. Also, the heat capacity of the reflective layer itself becomes large,
As a result, it takes time to cool the recording layer, which hinders the formation of amorphous marks. Most preferably, a reflective layer having a high thermal conductivity is thinly provided to selectively promote heat dissipation in the lateral direction. The quenching structure used in the past focuses only on the one-dimensional escape of heat in the film thickness direction, and is intended only to quickly escape the heat from the recording layer to the reflective layer.
No sufficient attention has been paid to the flattening of the temperature distribution in the plane direction.

The so-called "super-quenching structure in which the heat conduction delay effect in the second protective layer is taken into consideration" of the present invention, when applied to the recording layer of 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 during resolidification near Tm is the rate-determining factor for recrystallization. The ultra-quenching structure is effective for maximizing the immediate cooling rate in the vicinity of Tm to ensure the formation of the amorphous marks and the edges thereof, and the temperature distribution in the film surface direction. With the flattening, the high-speed erasing that was originally possible in the vicinity of Tm can surely secure the erasing 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 heat 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 instead, a guide can be obtained from thermal simulation and actual measurement results of recording sensitivity. As a material for the second protective layer having a low thermal conductivity which gives preferable results, at least one of ZnS, ZnO, TaS _{2 and a} rare earth sulfide is used in an amount of 50 mol% or more 9
Contains 0 mol% or less and has a melting point or decomposition point of 1000
A composite dielectric containing a heat-resistant compound having a temperature of ℃ or higher is desirable.

More specifically, a composite dielectric containing a rare earth sulfide such as La, Ce, Nd, or Y in an amount of 60 mol% to 90 mol% is desirable. Alternatively, the composition range of ZnS, ZnO or rare earth sulfide is 70 to 90 mol%.
Is desirable. Examples of heat-resistant compound materials having a melting point or decomposition point of 1000 ° C. or higher to be mixed with these are Mg, Ca, Sr, Y, La, Ce, Ho, Er,
Yb, Ti, Zr, Hf, V, Nb, Ta, Zn, A
l, Si, Ge, Pb and other oxides, nitrides, carbides and C
Fluorides such as a, Mg and Li can be used. In particular, materials that should be mixed with ZnO include Y, La, and C.
A rare earth sulfide such as e or Nd or a mixture of a sulfide and an oxide is preferable. 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, so the thickness is set to 30 nm or less. It is preferably 25 nm or less. When the thickness is less than 5 nm, the effect of delaying the heat conduction in the second protective layer portion is insufficient, and the recording sensitivity is significantly lowered, which is not preferable. The thickness of the second protective layer 4 is 15 nm to 25 when the wavelength of the recording laser light is 600 to 700 nm.
nm is preferable, and it is 5 to 2 when the wavelength is 350 to 600 nm.
0 nm is preferable, and more preferably 5 to 15 nm.

In the present invention, it has a very high thermal conductivity of 3
The feature is that the thin reflective layer 5 having a thickness of 00 nm or less is used to promote the heat dissipation effect in the lateral direction. In general, the thermal conductivity of a thin film differs greatly from the thermal conductivity in the bulk state and is usually small. In particular, in the case of a thin film having a thickness of less than 40 nm, the thermal conductivity may decrease by one digit or more due to the influence of the island structure at the initial stage of growth, which is not preferable. Furthermore, the crystallinity and the amount of impurities differ depending on the film forming conditions, which causes the difference in thermal conductivity even with the same composition.

In the present invention, the thermal conductivity of the reflective layer can be directly measured in order to define the reflective layer having a high thermal conductivity which shows good characteristics. You can estimate it. This is because the thermal conductivity and the electrical conductivity have a good proportional relationship in a material such as a metal film in which electrons mainly control heat or electrical conductivity. The electric resistance of a thin film is represented by a resistivity value standardized by the film thickness and the area of a measurement region. The volume resistivity and the area resistivity can be measured by a normal four-point probe method, and are defined by JIS K7194. This method provides much simpler and more reproducible data than actually measuring the thermal conductivity of the thin film itself. In the present invention, the reflective layer preferably has a volume resistivity of 20 nΩ · m or more and 150 nΩ · m or less, and more preferably 20 nΩ · m or more and 100 nΩ · m or less. A material having a volume resistivity of less than 20 nΩ · m is practically difficult to obtain in a thin film state. Even if the volume resistivity is larger than 150 nΩ · m, the area resistivity can be reduced by using a thick film having a thickness of more than 300 nm.
According to the study by the present inventors, a sufficient heat dissipation effect was not obtained even if only the area resistivity was lowered with such a high volume resistivity material. It is considered that the thick film increases the heat capacity per unit area. Further, such a thick film is not preferable from the viewpoint of manufacturing cost because it takes time to form the film and the material cost increases. Further, the microscopic flatness of the film surface is also deteriorated. It is preferable to use a low volume resistivity material that can obtain an area resistivity of 0.2 or more and 0.9Ω / □ or less at a film thickness of 300 nm or less. 0.5Ω / □ is the most preferable.

Materials suitable for the present invention are as follows. For example, it is an Al-Mg-Si based alloy containing Si in an amount of 0.3 wt% to 0.8 wt% and Mg in an amount of 0.3 wt% to 1.2 wt%. In addition, Ta, T
i, Co, Cr, Si, Sc, Hf, Pd, Pt, M
g, Zr, Mo, or Mn is 0.2 atomic% or more and 2 atomic%
The Al alloys contained below have an increased volume resistivity in proportion to the concentration of the additive element, improved hillock resistance, durability, and
It can be used in consideration of volume resistivity, film forming rate, and the like.
Regarding Al alloys, if the amount of added impurities is less than 0.2 atom%, the hillock resistance is often insufficient depending on the film forming conditions. If it is more than 2 atomic%, it is difficult to obtain the above low resistivity. When importance is attached to stability over time, Ta is preferable as an additive component. In particular, for the upper protective layer 4 containing ZnS as a main component, an AlTa alloy having Ta of 0.5 atomic% or more and 0.8 atomic% or less has corrosion resistance,
It is desirable as a reflective layer that satisfies all requirements of adhesion and high thermal conductivity in good balance. Further, in the case of Ta, addition of only 0.5 atom% makes it
A preferable effect in manufacturing that the film formation rate during sputtering is increased by 30 to 40%. When the above Al alloy is used as the reflective layer, the 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 it exceeds 300 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, the heat capacity of the reflective layer itself is large, and the cooling rate of the recording layer slows down. In addition, the microscopic flatness of the film surface also deteriorates.

Further, Ag, Ti, V, Ta, Nb,
W, Co, Cr, Si, Ge, Sn, Sc, Hf, P
An Ag alloy containing 0.2 atomic% or more and 5 atomic% or less of d, Rh, Au, Pt, Mg, Zr, Mo, or Mn is also desirable. When more importance is attached to stability over time, Ti and Mg are preferable as additive components. When the Ag alloy is used as the reflective layer, the preferable film 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 unnecessary thick films reduce the productivity. In addition, the microscopic flatness of the film surface also deteriorates.

The inventors of the present invention described above, the additive element to Al, A
It has been confirmed that the volume resistivity of the element added to g increases in proportion to the concentration of the element added. By the way, it is considered that addition of impurities generally reduces the crystal grain size, increases electron scattering at grain boundaries, and lowers thermal conductivity. It is necessary to adjust the amount of added impurities in order to obtain the original high thermal conductivity of the material by increasing the crystal grain size. The reflective layer is usually formed by a sputtering method or a vacuum evaporation method, but the total amount of impurities is 2 atomic% including not only the amount of impurities in the target and the evaporation material itself but also the amount of water and oxygen mixed during film formation. Must be: For this reason, it is desirable that the ultimate vacuum of the process chamber is 1 × 10 ⁻³ Pa or less. Further, if the film is formed at an ultimate vacuum degree lower than 10 ⁻⁴ Pa, it is desirable to prevent impurities from being taken in by setting the film formation rate to 1 nm / sec or more, preferably 10 nm / sec or more.

Alternatively, when the intentional additive element is contained in an amount of more than 1 atomic%, it is desirable that the film formation rate is 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 regardless of the amount of impurities. For example, in an alloy film in which about 2 atomic% of Ta is mixed with Al, an amorphous phase is mixed between crystal grains, but the ratio of the crystal phase and the amorphous phase depends on the film forming conditions. For example, as the sputtering is performed at a lower pressure, the proportion of crystal parts increases, the volume resistivity decreases, and the thermal conductivity increases. The impurity composition or crystallinity in the film 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 a thin film state is not determined only by the metal material and composition. To obtain high thermal conductivity,
As mentioned 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 make the reflective layer multi-layered in order to obtain higher thermal conductivity and higher reliability. At this time, at least one layer substantially controls the heat dissipation effect as the low volume resistivity material having a film thickness of 50% or more of the total reflection layer film thickness,
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 protective layer containing S, and tends to deteriorate a little when repeatedly overwritten. In addition, corrosion tends to occur in an accelerated test environment of high temperature and high humidity. Therefore, it is also effective to use Ag and Ag alloy as the low volume resistivity material and to provide an alloy layer containing Al as a main component between 1 nm and 100 nm inclusive as an interface layer with the upper protective layer. When the thickness is 5 nm or more, the layer does not have an island structure and is easily formed uniformly. As the Al alloy, as described above, 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% but not more than atomic% is included. If the thickness of the interface layer is less than 1 nm, the protective effect is insufficient, and 10
If it exceeds 0 nm, the heat dissipation effect is sacrificed. The use of the interface layer is particularly effective when the reflective layer is Ag or an Ag alloy. This is because Ag is relatively likely to be corroded by sulfidation when it comes into contact with the protective layer containing sulfide which is preferred in the present invention.

Furthermore, when the Ag alloy reflection layer and the Al alloy interface layer are used, since Ag and Al are a combination that is relatively easy to diffuse into each other, it is more preferable to oxidize the Al surface to a thickness of more than 1 nm to provide the interface oxide layer. preferable. If the interface oxide layer exceeds 5 nm, especially 10 nm, it becomes a thermal resistance, and the function as a reflecting layer having an extremely high heat dissipation property is impaired, 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 it also increases the target manufacturing cost and eventually the raw material ratio of the medium. Therefore, it is also effective to obtain a desired volume resistivity by forming a multi-layer of 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 3, the initial device cost may increase, but the individual medium cost may be suppressed rather. 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 multi-layered). Now, the thickness of the recording layer and the protective layer is good in the absorption efficiency of laser light in consideration of the interference effect due to the multilayer structure, in addition to the above-mentioned limitations in terms of thermal characteristics, mechanical strength, and reliability. It is selected so as to increase the amplitude of the signal, that is, the contrast between the recorded state and the unrecorded state.

For example, if the medium of the present invention is applied to a rewritable type DVD and compatibility with a read-only type DVD is ensured, the degree of modulation must be high. In addition, DPD (Differential P
It is necessary that the tracking servo method called hase detection) can be applied as it is. FIG. 6 shows D when the EFM plus modulated random signal is recorded and reproduced.
The waveform of the C reproduction signal (reproduction signal including a DC component) is shown.
The degree of modulation is defined as the ratio I ₁₄ / I _top of the signal intensity I _{top at} the top of the 14T mark and the signal amplitude I ₁₄ . I
_Top actually corresponds to the reflectance in the groove of the unrecorded portion (crystalline state). Regarding I _14, there is a problem in the intensity difference and phase difference of the reflected light from the crystal part and the amorphous part of the phase change medium. The difference in intensity of reflected light is basically determined by the difference in reflectance between the crystalline state and the amorphous state. When the degree of modulation after recording is about 0.5 or more, low jitter can be realized and the tracking servo by the DPD method also works well.

FIG. 7 shows the reflectance in a typical four-layer structure.
An example of calculating the difference is shown. On the polycarbonate substrate, (Z
nS)₈₀(SiO₂)₂₀Protective layer, Ge_0.05Sb_0.69Te
_0.26Recording layer, (ZnS)₈₀(SiO₂)₂₀Protective layer, Al
_0.995Ta_0.005A reflective layer was provided. Bending of each layer
The measured value is used for the folding rate. Each at a wavelength of 650 nm
The complex refractive index of the material is 2.12-0.0 for the upper and lower protective layers.
i, the reflective layer is 1.7-5.3i, the substrate is 1.56, recording
The layer is 3.5-in the amorphous state (measured immediately after film formation).
2.6i, 2.3-4.1i in crystalline state after initialization
It The recording layer, the second protective layer, and the reflective layer have different thicknesses.
Was kept constant at 18 nm, 20 nm and 200 nm. First
1 As far as the thickness dependence of the protective layer is seen, the amplitude change is usually small.
I, the denominator _top, That is, the reflectance of the crystalline state
Strongly depends. Therefore, the crystalline state reflectance is as low as possible.
Lower is desirable.

In the calculation example of FIG. 7, the first protective layer is a (ZnS) ₈₀ (SiO ₂ ) ₂₀ film having a refractive index n = 2.12.
At this time, the first minimum value d ₁ has a film thickness of 50 to 70 nm, and the second minimum value d ₂ has a film thickness of 200 to 220 nm. After that, it changes periodically. The film thickness of the first protective layer that minimizes the reflectance in the crystalline state is substantially determined only by the refractive index of the protective layer in the case of a recording layer having high reflectance. The minimum point film thickness at other refractive indices n can be almost obtained by multiplying d ₁ and d ₂ by 2.1 / n. Normally, the dielectric used as the protective layer is n
= About 1.8 to 2.3, and d ₁ is about 60 to 80 nm. 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 remarkably decreases, which is less than 0.5, which is not preferable. Conversely, 2.
If it is 3 or more, the reflectance of the minimum point becomes too low and is 20%.
Is not achieved and focus and tracking servo become difficult, which is not preferable.

In the composition range of the recording layer according to the present invention, as shown in FIG.
Optical characteristics almost similar to 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 film formation rate of the dielectric protective layer by the sputtering method is at most 15 nm / sec.
This is because spending more than a second increases the cost. Further, the allowable value of film thickness fluctuation becomes strict, which is not preferable in production. That is, as can be seen from FIG. 7, when the reflectance deviates from the desired film thickness d ₀ by Δd, it fluctuates by the same amount both in the vicinity of the first minimum value d _{1 and in the} vicinity of the second minimum value d ₂ .

On the other hand, the film thickness distribution in the manufacturing process usually has a uniformity limit of ± 2 to 3% with respect to d ₀ . Therefore, d ₀
The smaller the thickness, the smaller the variation width Δd of the film thickness, which is advantageous because it is possible to suppress the reflectance variation within the disc surface or between discs. Therefore, it is desirable to adopt a film thickness in the vicinity of the first minimum value d _{1 in} an inexpensive stationary facing type sputtering apparatus that does not have a substrate revolving mechanism. On the other hand,
Since the thick protective layer has a large effect of suppressing the deformation of the substrate surface at the time of repetitive overwriting, if it is important to improve the repetitive overwriting durability, it is preferable to adopt a film thickness in the vicinity of the second minimum value d _2. desirable. In a medium in which recording / reproducing light is incident through the substrate for recording or reproducing, the first protective layer must be thickened to some extent to protect the substrate from heat generated during recording. At the time of recording, the recording layer is about 100 nanoseconds, but 500 to 600 ° C.
That is all. For this purpose, the film thickness is preferably 50 nm or more. When the thickness is less than 50 nm, microscopic deformation is accumulated on the substrate when recording is repeated, which easily causes noise and defects. This is especially important when the substrate is made of a thermoplastic such as polycarbonate.

Next, a preferred optical recording method for use with this medium will be described. The preferred first recording method is
When recording mark length modulated information with a plurality of recording mark lengths on the recording medium described above, recording light having an erasing power Pe capable of crystallizing an amorphous material is irradiated between the recording marks to form one recording mark. When the time length of the recording mark is nT (T is a reference clock period, n is an integer of 2 or more), 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, 0 ≦ η ₁ + η ₂ ≦ 2.0
And α _i (1 ≦ i ≦ m) is a real number such that α _i > 0, and
β _i (1 ≦ i ≦ m) is a real number such that β _i > 0, and Σα _i <
0.5n. α ₁ = 0.1-1.5, β ₁ = 0.3
˜1.0, β _m = 0 to 1.5, and α _i = 0.1 to 0.
8 (2 ≦ i ≦ m). It should be noted that when i is 3 ≦ i ≦ m, α _i + β _i−1 = 0.5 to 1.5 and is constant regardless of i. ) In order, and α _i T
During the time of (1 ≦ i ≦ m), the recording light having the recording power Pw such that Pw ≧ Pe for melting the recording layer is irradiated, and within the time of β _i T (1 ≦ i ≦ m), 0 <P
b ≦ 0.2 Pe (however, in β _m T, 0 <Pb
The recording light having the bias power Pb of ≦ Pe) is irradiated.

By using this recording method together with the above-mentioned medium, the cooling rate of the recording layer at the time of re-solidification is accurately controlled, and at least 3 m / s to 8 m / s, and further 1 m / s depending on the setting of the recording conditions. In the wide linear velocity range of s to 15 m / s, the high-density mark length modulation recording with the shortest mark length of 0.5 μm or less is possible, repetitive overwriting of 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 the high density mark length modulation recording as described above, wavelengths of 350 to 680 are 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, NA is 0.55 or more and 0.
It should be 65 or less. If the NA exceeds 0.65, the influence of the aberration due to the inclination of the optical axis becomes large, and therefore it is necessary to make the distance between the objective lens and the recording surface extremely close. Therefore,
When the 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. 8, at least 3
By modulating the recording light power to a value, the power margin and the recording linear velocity margin can be widened. In FIG. 8, the start position of the _first recording pulse α ₁ T and the end position of the final off pulse β _m T do not necessarily have to match the start position and the 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 at the end. Fine adjustment of the length of η ₁ T or η ₂ T according to the length of the marks before and after the mark and the length between the marks is also effective for forming the marks accurately.

Alternatively, a good mark may be formed by changing only β _m according to the mark length nT. The final β _m may be 0. For example, EFM
As the longer mark such as 11T mark out of 3T to 11T mark in modulation or 14T mark out of 3T to 14T mark in EFM plus modulation is more likely to accumulate heat, the last β _m should be increased to shorten the cooling time. It is good to make it longer. On the contrary, in the case of a short mark such as a 3T mark, β _m should be shortened. The adjustment width is about 0.5. With high-density recording that exceeds the linear recording density of the so-called DVD, sufficient recording signal quality can be obtained without necessarily making 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 the temporal change of the temperature at one point on the recording layer when two recording pulses are irradiated. Recording pulse P1, off pulse, recording pulse P while moving the beam relative to the medium
2 is a temperature change at the position where the recording pulse P1 is irradiated when 2 is continuously irradiated. (A) shows the case where Pb = Pe and (b) shows the case where Pb≈0. Figure 9 (b)
Then, 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 in the middle is also high. Therefore, the amorphous mark is dissolved by the irradiation of the recording pulse P1 and is formed by the subsequent rapid cooling at the off pulse. On the other hand, in FIG. 9A, the erasing power Pe is applied even in the off-pulse period, so that 1
The cooling rate after the irradiation of the second recording pulse P1 is slow, and the minimum temperature TL reached by the temperature drop in the off pulse section is the melting point T.
The amorphous mark remains in the vicinity of m and is further heated to the vicinity of the melting point Tm by the subsequent recording pulse P2, so that an amorphous mark is hardly formed.

Taking a steep temperature profile shown in FIG. 9B for the medium of the present invention is important for suppressing crystallization in a high temperature region and obtaining a good amorphous mark. That's right. Because the recording layer of the medium of the present invention shows a large crystallization rate only in the high temperature region just below the melting point, the recrystallization is suppressed by taking the profile of (b) in which the recording layer temperature hardly stays in the high temperature region. This is because it is considered possible. Alternatively, the generation of crystal nuclei in a relatively low temperature region close to the crystallization temperature Tc is not dominant in each erasing process, and Sb clusters that can be the crystal nuclei formed during the above-described initialization are stably present. It is also considered that only crystal growth in the region is dominant. Therefore, by controlling the cooling rate and TL ′, recrystallization can be almost completely suppressed, an amorphous mark having a clear contour that substantially matches the melted region can be obtained, and jitter at the mark edge can be reduced.

On the other hand, in the GeTe-Sb ₂ Te ₃ pseudo-binary alloy, there is no great difference in the amorphous mark formation process in any of the temperature profiles of FIGS. 9A and 9B. This is because this material exhibits recrystallization in a wide temperature range, particularly in a low temperature region near the crystallization temperature Tc, although the rate is slightly slow. 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 in a wide temperature range as a whole. It is also possible that GeT
Even in e-Sb ₂ Te ₃ , coarse pulses may be suppressed by using an off pulse with Pb <Pe, but Pb / P
If e ≦ 0.2, the crystallization near Tc is excessively suppressed, so that the erasing performance deteriorates. However, in the recording layer material according to the present invention, it is considered that crystallization at a relatively low temperature close to Tc hardly progresses, so Pb / P
It is preferable that e ≦ 0.2. Alternatively, more specifically, it is better to set 0 ≦ Pb ≦ 1.5 (mW), use Pb that is as low as possible for tracking servo to be stable, and positively use an off pulse so that the cooling rate is as rapid as possible. Is preferable because the edge of is clearly formed.

In the pulse division method of FIG.
Recording pulse α at the tip₁Only T is the subsequent pulse α_iLonger than T
In addition, the off-pulse width β at the leading and trailing edges
₁T, β _mSet only T separately from other off-pulses
However, this is the most effective way to balance the characteristics of long and short marks.
It is valid. Cutting-edge pulse α₁T has no residual heat effect
Therefore, it takes a little longer for the temperature to rise. Alternatively,
The recording power of the leading pulse is higher than that of the following pulse
It is also effective to set.

Further, the pulse switching is performed in the clock cycle T
Pulse control becomes easier when synchronized with. FIG. 10 shows a pulse division method suitable for mark length modulation recording and having a simple pulse control circuit. As a pulse division method for recording the mark length modulation data in (a), (b) shows m = n−1, and (c) shows m = n−2. (B),
In (c), T is omitted to simplify the drawing. In both cases, α _i (2 ≦ i ≦ m) and β _i (2 ≦ i ≦ m−
1) is constant regardless of i, and 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. Further, making Pb the same as the reproduction light power Pr is also effective for simplifying the circuit. It is necessary to make only the _first pulse α ₁ T longer than the subsequent pulse in order to improve the recording balance between the short mark and the long mark in a so-called eye pattern. Alternatively, only the first pulse may have higher power than the subsequent pulses. Such a pulse can be achieved by determining three types of gate generating circuits as shown in FIG. 11 and priorities among them.

FIG. 11 shows pulse generation by the recording method of the present invention.
It is explanatory drawing of an example of a raw method. (A) is a clock signal,
(B) is a data signal, which is 3 in the recording pulse generating circuit.
Gate signal (c) Ga generated from the seed 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_iTies for generating a predetermined number of T (2 ≦ i ≦ m)
Decide ming. Where pulse width α _iIs in 2 ≦ i ≦ m
And a constant value α_cAnd Gate3 is an off pulse generation area
Between β _iGenerate T. Gate3 is on (high level)
Pb is generated during the period and Pe is generated during the off period (low level)
To do. α₁Only the rising timing and pulse width of
Β can be determined independently₁Β_iDifferent from
You can Gate3 and Gate1 have the same rise
It is good to expect. Gate1 and Gate2 are respectively
Pw is generated, but when Gates 1 and 2 are on, G
Take precedence over ate3. Gate1 delay time T₁When
α₁, Gate2 delay time (T ₁+ T₂) And α_cFinger
If specified, the strategy of FIG. 10 can be specified.

Here, assuming that T ₁ is 1T or more, FIG.
It becomes a pulse in the case of m = n−1 in (b), and if it is less than 1T and the number of subsequent pulses is reduced by one, m in FIG.
= N-2. At this time, by making α ₁ T and β _m−2 T longer than in the case of m = n−1, the mark length to be formed is 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 the read-only DVD and at least equal to that of the read-only DVD at the time of reproduction.

That is, it 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. Then, 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.

Keeping the ratio Pe / Pw constant is to widen the erasable range by increasing the erasing power when the power fluctuation occurs and the recording mark is large and the recording mark is large. When Pe / Pw is less than 0.3, Pe is always
Is low, and erasing tends to be insufficient. On the other hand, if it is larger than 0.6, Pe is excessive and re-amorphization is likely to occur at the beam center, and erasing by complete re-crystallization becomes difficult. Also,
The amount of energy applied to the recording layer becomes too large and is likely to deteriorate due to repeated overwriting.

The recording layer having the composition according to the present invention has α
_Since good jitter can be obtained in the range where _i is particularly small, Σ
It is desirable that α _i <0.5 n and that (Σα _i ) / n be decreased as k is smaller. That is, k = 0 or k =
In 1 (Σα _i) <0.4n, the k = 2 (Σα _i) <
It is preferably 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 , particularly y is 0.72 or more, and y is 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 2.57 or more, and more preferably 2.85 or more to be Sb rich.

In the present invention, the composition of the recording layer is
Even when rich, the amorphous mark has high stability and storage stability
Good property is one of the preferable characteristics. Special
In Kaihei 8-22644, Sb_0.7Te_0.3Neighborhood
A in which about 10 atomic% of Ag and In are added to the composition
A gInSbTe recording layer is described. But this
Sb / Te ratio of 2.57 or more in AgInSbTe recording layer
If so, the amorphous mark becomes extremely unstable and storage is stable.
There was a problem with sex. Below, a comparative explanation will be given using experimental examples.
It When performing mark length recording of EFM plus modulation,
A linear velocity of 2 m / s to 5 m /
In the range of s, the wavelength is 630 to 680 nm, NA =
The recording pulse is divided into n-1 pieces using the 0.6 optical system.
Then 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 above 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 the above AgInSbT.
Since the e recording layer also has almost the same optical constant, it is possible to obtain the same reflectance and modulation degree by using the same layer structure.
Therefore, a thermally equivalent layer structure 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, and 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) is preferred. Especially 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, Ag _0.05 Ge _0.05 Sb _{0.67 of the} present invention
In the Te _0.23 recording layer, α ₁ = 0.3 to 0.5, α _i =
The preferable 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 can be set. In this case, n = 3
, Σα _i ≈0.32n, and if n = 4 or more, Σα
α _i ≈0.33n to 0.34n. This means that, in the medium of the present invention, the average irradiation power irradiated at the time of recording can be reduced, and the substantial recording pulse irradiation time can be reduced to Σα _i <0.4n.

As a result, the following effects can be obtained. (1) The deterioration of the recording signal quality due to the high power recording can be reduced. The problem of high power recording is that the light energy applied to the recording layer is too much and stays in the recording layer. For this reason, the cooling rate becomes slow, recrystallization of the amorphous mark occurs, and deterioration during repetitive overwriting becomes significant. The average input power is suppressed by providing a low-power off-pulse section, and the heat is released in the plane direction by the high thermal conductivity reflective layer, so that even at the time of high power recording, the trailing edge of the mark, especially the trailing edge of the long mark It is possible to suppress the adverse effect of the heat accumulation of, and to form a good long mark. (2) It is possible to reduce the thermal damage to each layer during repeated overwriting and improve the repeated durability. By reducing the heat damage each time, for example, the deformation of the plastic substrate, which is weak against heat, can be suppressed. Further, the range of damage can be limited to a narrower range in the central portion of the laser beam profile. Particularly, heat is likely to be accumulated n = 4
The longer mark has the greater effect of reducing the actual recording energy irradiation rate (Σα _i ) / n. Therefore, even at a low linear velocity of 5 m / s or less that is easily damaged by heat, the adverse effect on the medium can be reduced.

In the present invention, it is possible to improve the repetitive overwrite durability as described above, and it is possible to achieve the number of overwrites which is one digit or more larger than the conventional one. Furthermore, the recording layer is
_{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) and by changing the recording pulse division method according to the linear velocity, overwriting is possible 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 = n−k is kept constant, and either Pb / Pe or α _i is monotonically decreased as the linear velocity at the time of overwriting decreases. The clock cycle may be changed according to the linear velocity in order to keep the recording linear density constant, or the Pw and Pe may be changed so as to be optimal at each linear velocity. .

The present invention further provides a method for recording a so-called EFM plus modulation signal having a minimum mark length of 0.35 to 0.45 μm at both the 1 × speed and the 2 × speed of the standard playback linear velocity of DVD. To do. The standard reproducing linear velocity of DVD is 3.49 m / s. That is, the light having a wavelength of 600 to 680 nm and the numerical aperture NA of 0.55 to
An optical recording method of recording and reproducing data by passing through a 0.65 objective lens, focusing on a recording layer through a substrate, and setting a 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 ≦
Within the range of Pb ≦ 1.5 (mW), constant regardless of the linear velocity,
Pe / Pw is assumed to be variable in the range of 0.4 to 0.6 according to the linear velocity. (I) In the range of the recording linear velocity of 3 to 4 m / s, the reference clock period 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), β _m = 0.3 to 1.5, and the recording light of the recording power Pw ₁ is set within the time of α _i T (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 .5 and constant regardless of i (2 ≦ i ≦ m), α ′ _i + β ′ _i−1 = 1.0 (3 ≦ i ≦ m), β ′ _m = 0 to 1.0, and α _When 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 ≦
The optical recording method is Pw ₁ / Pw ₂ ≦ 1.2. According to the experiments conducted by the inventors, as long as the pulse division method shown in FIG. 10 is used, particularly good jitter can be obtained with this setting.

Here, if α ₂ + β ₁ = 1.0, the independent parameters relating to the pulse width are α ₁ , α _i , β
_{The number of m} is three, which is preferable because the recording signal source can be further simplified. Note that it is not necessary to take all integers from 1 to 14 as n, and take 3 to 11 and 14 in EFM plus modulation. (1,7) RLL-NRZI (Ru
n Length Limited-Non Return To Zero Inverted) code or the like can also be used. In order to keep the recording density constant, generally, the clock cycle at the 1 × speed recording is set to be double that at the 2 × speed recording. According to the present invention, not only the method of recording on the entire recording area while maintaining the constant linear velocity (constant linear velocity, CLV method) as described above, but also the recording is performed on 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) method in which the radial direction is divided into a plurality of zones and the CLV method is used for overwriting in the same zone. The diameter of the optical disc is 86m
m, 90 mm (single CD size), 120 mm (C
D size) or 130 mm, and the recording area extends from a radius of 20 to 25 mm to a maximum of 65 mm. At this time, the linear velocity difference between the inner and outer circumferences is nearly tripled.

Generally, in high-density mark length recording, the linear velocity range in which the phase change medium exhibits good overwrite characteristics is a range of about 1.5 times the linear velocity ratio. If the linear velocity is high, the cooling rate of the recording layer is high, so that amorphous marks are easily formed, but the time for keeping the temperature above the crystallization temperature is short and erasing becomes difficult. On the other hand, if the linear velocity is slow, erasing is easy, but the cooling rate of the recording layer is slow, so recrystallization is likely to occur and a good amorphous mark is difficult to form. In order to solve this problem, it is possible to adjust the thickness of the reflective layer at the inner and outer circumferences so that the heat dissipation effect by the reflective layer is increased at the inner circumference. Alternatively,
It has also been proposed to change the composition of the recording layer to increase the crystallization rate at the outer circumference or decrease the critical cooling rate required for amorphous formation at the inner circumference. However, it is not easy to make a disc having such a distribution.

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

That is, an optical system having a predetermined recording area
By rotating the information recording medium at a constant angular velocity
This is a method of recording by the mark length, and the innermost circumference of the recording area
The linear velocity at 2 to 4 m / s and the line at the outermost periphery of the recording area
The medium is rotated so that the speed is 6 to 10 m / s,
The recording area consists of multiple zones separated by a radius.
The recording density is almost equal to the average linear velocity in each zone.
The reference clock cycle T is changed so as to be constant. this
At this time, the pulse division number m is set to be constant regardless of the zone,
From the zone to the inner zone, the Pb / Pe ratio and /
Or α_i(I is at least one of 1 ≦ i ≦ m) monotonically
Reduce. As a result, it is possible to reduce the
Incomplete formation of amorphous marks due to insufficient cooling rate.
Can be prevented. Note that α _i(I is 1 ≦ i ≦
monotonically decreasing (at least one of m)
If α₁, Α₂, ..., α_mIn₂Reduce only
It means that. More specifically, the pal shown in FIG.
Pulse division method based on the linear velocity
Using can simplify the variable pulse division method circuit.
It is desirable to be able to. At that time, the recording area in the radial direction
Divide into p zones and clock period for each zone
And changing the pulse division method depends on the radial position.
It is easier than changing continuously.

In the present invention, the recording area is divided into p zones by the radius, the innermost side is the first zone, the outermost side is the p-th zone, and the q-th zone (where q is 1 ≦ q ≦
(integer of p), the angular velocity is ω _q , and the average linear velocity is <v _q
> _Ave , maximum linear velocity <v _q > _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 a range of _{1.2~3, <v q> max /} <v
_It is preferable that _q > _min be 1.5 or less. The same clock cycle and the same pulse division method are used in the same zone, but the linear velocity range that can be covered by the same pulse division method is about 1.5 times the limit.

Then, within the same zone, ω _q , T _q ,
α _i , β _i , Pe, Pb, and Pw are constant, and the physical length of the shortest mark n _min T _q <v _q > _ave is 0.5 μ.
m or less, T _q <v _q > _ave is almost 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 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. Here, when m = n−1, α ₁ = 0.3 to
1.5, α _i = 0.2 to 0.5, and α when m = n−2
It is preferable to set ₁ = 0.5 to 1.5 and α _i = 0.4 to 0.8.

It is important to change the pulse division method according to the following law. Pb, P for each zone
w, Pe / Pw ratio, α _i , β ₁ , and β _m are variable, and at least α from the outer zone to the inner zone.
_i (i is at least one of 2 ≦ i ≦ m) is monotonically decreased. The change of α _i for each zone is preferably in steps of 0.1T or 0.01T. Here, with respect to the reference clock period T _p in the outermost zone, 1/10
By adding a high frequency base clock generation circuit having a cycle of about 0, T _q and divided pulse lengths in all zones can be generated as a multiple of this base clock. In DVD, the standard clock frequency at 1 × speed is about 26 MHz, so the maximum base clock frequency is about 2.6 GHz, which is usually one digit less than 260 MHz.
A base clock frequency on the order of z is sufficient.

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

In the present invention, the optical head
Virtually set a zone on the recording medium from the radial position information
May be recorded on the disc or recorded on the disc in advance.
According to the registered address information and zone information.
A zone structure may be physically provided on the mask. Virtual
Linear velocity, whether physical or physical
It suffices to select a recording pulse division method according to the above. next,
Another example in which the optical recording method of the present invention is applied to the ZCAV system.
I will describe. Recording area has p zones depending on the radius
The innermost side is the first zone and the outermost side is the p-th zone.
And the q-th zone (where q is 1 ≦ q ≦ p
The angular velocity at_q, Average linear velocity <v
_q>_ave, The maximum linear velocity <v_q>_max, The minimum linear velocity <
v_q>_min, The reference clock period is T_q, At the shortest mark
The interim length is n _minT_qAnd In ZCAV system
Is the outer zone so that the recording linear density is almost constant.
To the reference clock T of the recorded data._qSmall
It is necessary to drill. That is, T_q<V_q>
_aveIs almost constant for all q where 1 ≦ q ≦ p
, Depending on the zone_qChange. Where
To be almost constant includes an error of about ± 1%. Well
Also, the maximum and minimum linear velocities within the same zone are within a certain range.
In order to

[0128]

(14) (< _vq > _max- < _vq > _min ) / (< _vq > _max + < _vq > _min ) <10% (2)

The width of the zone is determined so as to satisfy the above. That is, (< _vq > _max- < _vq > _min ) becomes (< _vq >
_max + <v _{q> min)} to be less than 10% of the width of the q zones shall to a radius position of less than ± 10% of the average radius <r _{q> ave} is allowed. More preferably, (< _vq > _max- < _vq > _min ) is (< _vq > _max
It is less than 5% of + <v _q > _min ). The width of the zone may equally divide the recording area 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 studies made by the present inventors, the jitter value was at a practical level even if the shortest mark length was about 0.4 μm and the expression (2) was satisfied. The above two conditions are conditions for making the recording linear density constant, and thus making the physical length of the mark or the channel bit length constant. The channel bit length is the length per channel bit along the track. In order to obtain reproduction compatibility with DVD more reliably, the reference reproduction speed v is 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 is approximately less than ± 1%. To satisfy this condition in the ZCAV medium, the following formula (3) is used.

[0131]

(15) (< _vq > _max- < _vq > _min ) / (< _vq > _max + < _vq > _min ) <1% (3)

The following must be satisfied. That is, (<v
_q > _max- < _vq > _min ) is (< _vq > _max + < _vq >
_min ), and the width of the q-th zone is
It is assumed that a radius position of less than ± 1% of the average radius <r _q > _ave is allowed. Therefore, the recording area is divided into 200 or more zones. And,

[0133]

(16) T _q <v _q > _ave = vT (4)

That is, T _q <v _q > _ave is set to be substantially constant for all q where 1 ≦ q ≦ p. Here, “substantially constant” includes an error of about ± 1%. As a result, pseudo-uniform density recording independent of the radius can be performed in spite of the ZCAV system, so that the CLV system can be reproduced and the compatibility with the CLV system DVD player is enhanced. If desired, the zone width may be narrower.

Under the above conditions, the DVD
An optical recording method for obtaining a recording density equivalent to that of will be described.
Light with a wavelength of 600 to 680 nm has a numerical aperture NA of 0.5.
When recording and reproducing data by converging on the recording layer through the substrate through the objective lens of 5 to 0.65, the innermost circumference of the recording area is in the range 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 of the innermost circumferential zone is 3 to 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
_{q> max,} the 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, n is an integer of 1 to 14, m = n- 1 and ω
_q , Pb and Pe / Pw are constant regardless of the zone,
T _q <v _q > _ave is almost constant for all q _satisfying 1 ≦ q ≦ p, and

[0136]

(17) (< _vq > _max- < _vq > _min ) / (< _vq
> _Max + < _vq > _min ) <10%

(I) In the first zone, α ¹ ₁ = 0.3 to 0.8, α ¹ ₁ ≧ α ¹ _i = 0.2 to 0.4, which is constant regardless of i. (2 ≦ i ≦ m), α ¹ ₂ + β ¹ ₁ ≧ 1.0, α ¹ _i + β ¹ _i-1 = 1.0 (3 ≦ i ≦ m), and (i
i) In the p-th zone, α ^p ₁ = 0.3 to 0.8,
α ^p ₁ ≧ α ^p _i = 0.3 to 0.5, which is constant regardless 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 is recorded as a value between α ¹ ₁ and α ^p ₁ .

The innermost circumference of the recording area has a radius of 20 to 25 m.
When the radius is in the range of m and the outermost radius is in the range of 55 to 60 mm, the radius width of the recording area is about 30 to 40 mm. Then, in the innermost first zone of the disc,
v _{1> ave} = rotate at a constant angular velocity so that 3 to 4 m / s. Recording is performed under the above conditions for the first zone and the p-th zone, and the other zones (the q-th zone with 2 ≦ q ≦ p−1) are recorded.
Zone), α ¹ _i ≤α ^q _i ≤α ^p _i (2≤i≤
m) and α ^q ₁ is a value between α ¹ ₁ and α ^p ₁ .
In this case, it is desirable to set the value of α ^q ₁ in steps of 0.1T or 0.01T. Preferably α ¹ ₁ ≧ α ^q
Let ₁ ≧ α ^p ₁ (where α ¹ ₁ > α ^p ₁ ).

Furthermore, Pb, Pe / Pw, β₁, Β_mIs
It is constant regardless of the zone and α₁, Α_iOnly in the zone
By changing more, the linear velocity of 3-8m / s is fully covered.
To obtain good overwrite characteristics in a wide linear velocity range
You can Preferably, these Pe / Pw, Pb, P
w, β_m, (Α¹ ₁, Α^p ₁), (Α ¹ _c, Α^p _c) Number
The value is pre-pit row or groove deformation on the substrate in advance
By describing by, each recording medium and each
Drive and pulse division method and power optimized for each zone
You may be able to select These are usually recorded
Record at a position adjacent to the innermost or outermost edge of the area
To be done. Bias power Pb equal to playback power Pr
If so, do not enter the bias power Pb.
In some cases it may be okay. Specifically, groove deformation means groove meandering.
(Wobble) etc.

Alternatively, the optical information recording medium in which the address information is recorded in advance on the substrate by the pre-pit row or the groove deformation includes the address information and the information about appropriate α ₁ and α _{i at the} address. Good. As a result, when accessing, the pulse division method information can be read together with the address information, and the pulse division method can be switched. The pulse division method suitable for the recording medium and the zone to which the address belongs without any special correction. Can be selected.

The method of recording over the entire circumference of the disc while changing the recording pulse division method for each zone as described above is also applicable 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, 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 the recording area is divided into a plurality of radial zones, but in the same zone, recording is performed in the CLV mode, that is, while rotating the disc at a constant linear velocity.

Therefore, when the recording method of the present invention is applied to the ZCLV system, when the linear velocities of the innermost peripheral zone and the outermost peripheral zone are V _in and V _out , respectively, the difference between V _in and V _out is small. However, by setting V _out / V _in to 1.2 to 2, the burden of linear velocity dependence on the medium is reduced. The medium of the present invention can record in a wide range of linear velocities of 3 to 8 m / s by slightly changing the recording pulse division method.
The ZCLV method of dividing into a relatively small number of zones can be applied. At this time, in order to obtain the uniform recording density regardless of the zones, the linear velocity V _q in each zone and the reference clock period T _q of the recording data in each zone are expressed by T _q <v _q > _ave q.
It is almost constant regardless of

Then, in each zone, optimized
The 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
₁Set T, Pe / Pw, and Pb constant, depending on the linear velocity
Α_iAnd / or β_mRecording by changing
U The CLV method, ZCAV method, or Z described above
In the CLV method, depending on the linear velocity during overwriting
The example of making the recording pulse division method variable is mainly β _mTo
Simplify the pulse generation circuit by keeping constant regardless of linear velocity
It was something, but conversely, β_mTo actively change
Therefore, it is also possible to simplify the pulse generation circuit.
It

That is, in recording the information with a plurality of recording mark lengths of the shortest mark length of 0.5 μm or less, with the crystal part in the unrecorded / erased state and the amorphous part in the recorded state,
An erasing power P capable of crystallizing an amorphous material is provided between recording marks.
When the recording light of e is irradiated and the temporal length of one recording mark is nT (T is a reference clock period, n is an integer of 2 or more), the temporal length of the recording mark is nT.

[0145]

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, 0 ≦ η ₁ + η ₂ ≦ 2.0
And α _i (1 ≦ i ≦ m) is a real number such that α _i > 0, and
β _i (1 ≦ i ≦ m) is a real number such that β _i > 0. α ₁ =
0.1-1.5, β ₁ = 0.5-1.0, β _m = 0
And 1.5 for 2 ≦ i ≦ m, α _i is 0.1
It is in the range of 0.8 and is constant regardless of i. Note that α _i + β _i-1 is 0.5 to 0.5 for _{i where} 3 ≦ i ≦ m.
It is in the range of 1.5 and is constant regardless of i. )
In the time of α _i T (1 ≦ i ≦ m), recording light having a recording power Pw of Pw> Pe for melting the recording layer is irradiated, and β _i T (1 ≦ i ≦ m). within) time, 0 <Pb ≦ 0.2Pe (However, in the β _m T, 0 <irradiated with recording light of Pb ≦ Pe and could be) made bias power Pb, m irrespective of the linear velocity, alpha _i +
β _i-1 (3 ≦ i ≦ m), α ₁ T, and α _i T (2 ≦ i ≦
In this optical recording method, m) is kept constant and β _m monotonically 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 period T is changed in inverse proportion to the linear velocity. Then, by keeping α _i + β _i-1 constant at least in 3 ≦ i ≦ m, preferably 2 ≦ i ≦ m, regardless of the linear velocity and i, the pulse generation circuit can be simplified, and α _i Can be monotonically decreased as the linear velocity decreases to increase the cooling rate of the recording layer. Normally, α _i + β _i-1 = 1.0. In order to realize such a pulse division method, in the diagram for explaining the gate generation timing in FIG. 11, the width α ₁ T is synchronized with the reference clock cycle T (a constant delay may be added). One fixed length pulse (Gat
e1) and a plurality of subsequent fixed length pulses (Gate2) of width α _i T (α _c T) are generated, and only Gate3 that 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, Minimum recording power is Pw _minWhen Pw_max/ Pw_min≦ 1.2, Pe / Pw = 0.4 to 0.6, 0 ≦ Pb ≦ 1.5 (mW) Is preferred. Also, as mentioned above, at least
When the linear velocity during overwriting is 5 m / s or less
To prevent thermal damage during repeated overwriting
, And when m = n−1, Σα_i<0.4n, m =
Σα for n-2_i<0.5n is preferred
Yes.

[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
As β _m at the linear velocity at each overwrite
A value between ^L _m and β ^H _m , regardless of the recording linear velocity, Pb,
A recording method in which the Pe / Pw ratio is constant can be applied. In this case, at least the Pe / Pw ratio, Pb, Pw,
If the numerical values of α ₁ T, α _i T, (β ^L _m , β ^H _m ) are recorded beforehand on the substrate of the medium by the prepit train or the groove deformation, the optimum pulse division method is automatically selected. It can be selected and preferred.

Furthermore, if the maximum linear velocity is up to about twice the minimum linear velocity, an optical recording method in which β _m is constant regardless of the recording linear velocity while maintaining sufficiently practical signal quality. Is also possible. In a CLV system read-only DVD drive, a data clock and a rotation synchronization signal are generated based on a reference clock cycle obtained by reproducing a mark,
There is a method of controlling rotation.

As described above, the medium on which the mark is recorded by the ZCAV system so that the shortest mark length or the channel bit length is almost constant irrespective of the recording radius is a read-only DVD drive of this system. 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 marks substantially matches the reference data clock Tr of the drive.
Since the rotation synchronization control can be performed by the (PhaseLock Loop) method, even if there is some fluctuation in the linear velocity or fluctuation in the channel bit length, the reproducing circuit can directly decode the fluctuation.

In particular, 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 the rotation synchronization signal generated from the recorded mark. At the same time, a reference data clock Tr having a frequency in the range of 25 to 27 MHz is generated, and based on this clock, it can be reproduced as a CLV recording medium without being aware of the transition between zones. Of course, if rotation synchronization is achieved such that the reference data clock becomes Tr / 2, reproduction at double speed becomes possible. Such P
For the rotation synchronizing signal generation circuit and the like according to the LL system, the system of the already known DVD player or DVD-ROM drive can be used as it is.

By the way, the medium of the present invention can secure the reproduction compatibility with the DVD in all the signal characteristics except 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 during reproduction becomes small. Therefore, the groove depth is set to λ / (8
It should be shallower than n). It should be noted that λ is the reproduction light wavelength in air, and n is the refractive index of the substrate. However, since a push-pull signal is normally used for tracking servo during recording, it is not preferable if it is too small.

Regarding the reproduction signal characteristic, high CN
In order to obtain the ratio, the modulation Mod is preferably 0.5 or more. However, Mod is (amplitude of envelope of DC reproduction signal) / (upper limit of envelope of DC reproduction signal). A preferable groove depth is d = λ / (20n) to λ
/ (10n). If it is too shallow than λ / (20n),
The tracking pull 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.
The range of m is desirable.

Further, in order to secure the same capacity as that of the DVD, the groove pitch is set to 0.6 to 0.8 μm. If the groove pitch is 0.74 μm, compatibility with DVD is easy to obtain. The groove width is preferably 0.25 to 0.5 μm. If it is narrower than 0.25 μm, the push-pull signal becomes too small. If it is wider than 0.5 μm, the width between the grooves becomes narrow, and it is difficult for resin to enter during injection molding of the substrate,
It becomes difficult to accurately transfer the groove-shaped substrate. The medium of the present invention has a low reflectance after recording. In such a medium, in order to lower the reflectance in the groove, that is,
In order to set the average reflectance in the groove after recording to RGa and the average reflectance between the grooves after recording to RLa so that RGa <RLa, the groove width is preferably narrower than the groove width.

For example, if the groove pitch is 0.74 μm for compatibility with DVD, it is preferable that the groove width is narrower than 0.37 μm which is half of the groove width. On the other hand, when the average reflectance in the groove before recording is RGb and the average reflectance between the grooves before recording is RLb, and if RGb> RLb may be satisfied as long as the above RGa <RLa is satisfied, the groove Set the width to 0.
When the thickness is 4 to 0.5 μm, the width of the amorphous mark recorded in the groove may be increased, the degree of modulation may be increased, and the jitter may be reduced. Now, these grooves may be provided with periodic deformation in order to access an unrecorded specific track and to obtain a synchronization signal for rotating the substrate at a constant linear velocity. Generally, a wobble that meanders in the 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 taken out by the PLL method. The groove meandering amplitude is 40-80
nm (peak-to-peak value) is desirable. If it is less than 40 nm, the amplitude is too small and the SN ratio becomes worse. If it exceeds 80 nm, the upper and lower ends of the envelope of the recording signal shown in FIG. turn into.
When the wobble frequency is close to the band of the recorded data, its amplitude is preferably 80 nm or less.

Further, if the meandering frequency-modulated or phase-modulated according to the specific address information is formed by using the meandering frequency f _wo as a carrier wave, the address information can be obtained by reproducing the meandering. If the groove meandering is formed with the meandering frequency f _{wo kept} constant, the reference clock signal T for data can be generated from the reference period T _w of the groove meandering signal generated from f _wo or a multiple or divisor thereof.
Usually, the wobble period is set to be 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 bandpass filter or the like. In particular, setting f _wo to be lower than the reference clock cycle of data by about 1 to 2 digits has been put to practical use in recordable CDs and the like. In the medium used for the CLV system, PL
After L rotation synchronization is achieved, f _wo is multiplied by about 1 to 2 digits to generate a data reference clock. The data reference clock generated by such a method is generally accompanied by fluctuation of the same order as the data reference clock (frequency) due to the influence of fluctuations in rotation synchronization (about 0.1 to 1% of f _wo ). Cheap. This worsens the window margin for data detection.

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

[0159]

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 changing the frequency f _wo for each zone and forming the groove meander at a constant angular velocity, f
The reference clock or multiplication factor frequency that is generated as _wo, can be generated as the reference clock T _q for the data. At this time, if the wobble of the groove is set to a relatively high frequency that satisfies the expression (5), it becomes easy to generate the data reference clock for each zone. Then, the reference clock T _q can be changed for each zone and the variable pulse division method can be generated in synchronization with this signal, and the positional accuracy and fluctuation of each divided pulse can be reduced, which is preferable. As an example of ZCAV system zone division, it is conceivable that one circumference of the groove is set as one zone. At this time, if the groove has a wobble with a constant cycle regardless of the zone, the groove pitch is TP, and the meandering cycle is Tw ₀ , approximately

[0161]

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

By satisfying the following relation, the period Tw
A wobble having a constant _{value of 0} is formed over the entire recording area, and the number of a wobbles increases every time the track makes one outer circumference. Then, Tw ₀ is an integral multiple of the reference clock period T, that is, Tw ₀
It is desirable that = mT (m is a natural number) can be simplified because the reference clock generation circuit can be simplified because it can be simply divided by an integer when the reference clock is generated from Tw ₀ . In this case, m does not have to be an approximate 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, which is approximately the wobble period.
Tw ₀= 35T, wobbles included in each round
The number of is increasing one by one. In this case, the CLV method
In spite of the introduction of wobbles,
Interference because the wobble phase of the rack is always aligned
The fluctuation of the reproduction amplitude of the wobble signal due to (beat) is small
There is an advantage.

The application examples of the present invention have been described above.
The present invention is effective for improving the linear velocity dependence and recording power dependence in mark length recording of general phase change media, and is not limited to rewritable DVDs. 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 mark stability. In that case, it should be noted that the temperature distribution in the track crossing direction is flattened, and the film thickness of the second protective layer is 5 to 15 nm.
It is effective to make it extremely thin. Wavelength 350-45
When using 0 nm laser light, it is more preferable that the thickness be 10 nm or less.

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

[0166]

EXAMPLES Examples will be shown below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.
In the examples below, the substrates were made by injection molding. The substrate is a 0.6 mm thick injection-molded polycarbonate resin substrate, unless otherwise specified, the groove pitch is 0.74 μm,
A groove having a width of 0.34 μm and a depth of 30 nm formed on a spiral was used. Unless otherwise specified, the groove has a linear velocity of 3.
At 5 m / s, the wobble has a frequency of 140 kHz and the wobble amplitude is about 60 nm (peak-to-p).
eak value).

The groove shape was measured by an optical diffraction method that approximates the U groove. The groove shape may be measured by a scanning electron microscope or a scanning probe microscope. In this case, the groove width at half the groove depth is used. Unless otherwise specified, after forming a four-layer structure as shown in FIG. 5A on the substrate,
A protective layer made of UV curable resin is spin-coated on top of this, and another 0.6 mm with the same layer structure.
It was bonded to a thick substrate. In addition, 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 film formation is amorphous and has wavelengths 810 to 8 focused on the major axis of about 90 μm and the minor axis of about 1.3 μm.
Linear velocity of 3.0 to 6. with a laser beam of 30 nm.
An appropriate linear velocity was selected within the range of 0 m / s, and irradiation with light having an initialization power of 500 to 700 mW was performed to melt and recrystallize the entire surface to give an initial (unrecorded) state. The composition of each layer was confirmed by combining fluorescent X-ray analysis, atomic absorption analysis, X-ray excitation 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 thickly on the substrate to have a thickness of several hundreds nm. The film thickness was used by calibrating the fluorescent X-ray intensity with the film thickness measured by a stylus meter. The sheet resistivity of the reflective layer is a 4-probe resistance meter {L
oresta FP, (trade name) manufactured by Mitsubishi Petrochemical (now Dia Instruments). The resistance was measured on a reflective layer formed on a glass or polycarbonate resin substrate which is an insulator, or on the uppermost reflective layer after film formation with the four-layer structure (before UV-curing resin protective coating) of FIG. . Since the upper protective layer is a dielectric thin film and an insulator,
Even the four-layer structure does not affect the measurement of the sheet resistivity of the reflective layer. Also, a diameter of 1 that can be regarded as a virtually infinite area
The measurement was carried out with the 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 formulas.

[0169]

(21) ρs = F · R (6) ρv = ρs · t (7)

Here, t is a film thickness, 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 stated, a DDU1000 evaluation machine 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. The beam diameter corresponds to a region where the energy intensity of the Gaussian beam is 1 / e ² or more of the peak intensity.

Recording is performed by the pulse division method shown in FIG.
Unless otherwise specified, m = n−1, α _i + β _i−1 = 1.
It was set to 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
Unless otherwise specified, w was fixed at 0.5. Pb
The modulation degree and the jitter were measured while keeping the value constant between 0.8 and 1.0 mW and changing Pw. The signal to record is a DVD
8-16 modulation (EFM plus modulation) used as the random signal, and the shortest mark length was 0.4 μm unless otherwise specified. Unless otherwise specified, the measurement was performed with only a single track recorded.
The effect of crosstalk is not included. Recording was performed at various linear velocities such as 1 × and 2 ×, with the standard linear velocity of 3.5 m / s of DVD being 1 ×.

The reproduction was always performed at a linear velocity of 3.5 m / s, and the jitter was measured after binarizing the reproduction signal after passing through the equalizer. Jitter refers to edge-to clock jitter, and the measured value is expressed as% of the reference clock period T. The characteristics of the equalizer comply with the read-only DVD standard. Reference clock cycle T =
38.2 nsec. (26.16 MHz), jitter of less than 10% (more preferably less than 8%), and 5
It is preferable to obtain a modulation degree of 0% or more, preferably 60% or more. Furthermore, there is little increase in jitter after repeated overwriting, and after at least 100 times,
Preferably, it is desirable to be able to maintain less than 13% with respect to T even after 1000 times. From the standpoint of ensuring compatibility with read-only DVDs, measurement with reproduction light at 650 to 660 nm is important, but in the present invention, the wavelength only slightly affects the focused light beam shape. If the reproduction optical system is adjusted, 637n as used in the present invention can be obtained.
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 a recording layer,
InGeSbTe system according to the present invention and conventionally known InAg
In order to compare with the SbTe quaternary system, a medium having almost exactly the same recording layer composition and layer constitution other than the composition of Ag and Ge was prepared as shown in Table 1. The composition of both recording layers is within the range of measurement error except that Ag and Ge are replaced, and the composition is within a range that can be considered sufficiently equivalent. The thickness of the lower protective layer is different because the reflectance Rtop of the medium is adjusted to be the same. This kind of correction is necessary because the refractive index of the recording layer is slightly different, but in order to make the same absorption efficiency of light to the recording layer and the same effect of thermal damage due to reproducing light, to compare. Is the necessary correction.
Since the recording layer thickness and the upper protective layer thickness are the same, the heat radiation effect and the heat damage can be regarded as equivalent. The substrate is a 0.6 mm thick polycarbonate resin with a groove pitch of 0.
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. I went.

[0174]

[Table 1]

Recording was performed on these two types of media by EFM plus modulation at a recording linear velocity of 3.5 m / s and T = 38.2 nanoseconds. As a result, good overwrite recording characteristics were exhibited. The overwrite recording conditions were not the conditions in which the characteristics of the respective disks were necessarily the best, but the common characteristics were such 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 =
It was set to 0.8 mW. The signal recorded in this manner was repeatedly irradiated with reproducing light to examine the stability of reproducing light. After irradiation with a predetermined reproduction light power Pr a predetermined number of times, the reproduction light power was sufficiently lowered to 0.5 mW to measure the jitter and the like. Results are shown in FIG. The medium of Example 1 has a reproduction light power of 1
With mW, no deterioration due to reproducing light was shown up to 10 ⁶ 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
The first 100 to 1 in all reproduction light above mW
The jitter increases abruptly up to 000 times and then gradually worsens. The jitter value is high as a whole, but the initial deterioration of jitter is fatal. In Comparative Example 1, the degree of modulation was also lowered by the reproducing light, and after irradiation about 100 times, it was lowered by about 10% and stabilized. Jitter increases rapidly at the beginning,
It is considered that the decrease in the degree of modulation proceeds nonuniformly. The recorded media of Example 1 and Comparative Example 1 were mixed at 80 ° C./80% R
When it is left in the environment of H and an acceleration test is performed, it is 25
After 0 hours, the characteristics of the disk of Example 1 hardly changed at all, whereas the recording signal of the disk of Comparative Example 1 disappeared almost completely. 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 the initial overwrite recording characteristics but also in stability against reproduction light and stability over time. This is Sb _0.7 T
It has been shown that the addition of an appropriate amount of Ge is very effective in an alloy system containing an excess of Sb in e _0.3 . The medium of Example 1 was subjected to an acceleration test under an environment of 80 ° C./80% RH. The accelerated test was carried out up to 2000 hours.
The deterioration of the jitter of the signal recorded before the acceleration test was only about 1%. In addition, the degree of modulation was 64% in the initial stage, but was 61% even after the 2000-hour acceleration test, which was almost unchanged. The reflectance was almost unchanged. The deterioration of jitter was about 3% when recording was newly performed on the unrecorded area after 2000 hours, but this is at a level that causes no practical problems. In the medium of the first embodiment, the dependence of jitter on the recording pulse division method is m = n−1.
And m = n−2 were examined in detail.

FIG. 13 shows that at a linear velocity of 3.5 m / s.
When recorded at (a) m = n-1 and (b) m = n-2, respectively.
Α of the total jitter₁, Α_cIt is a contour map showing the dependence
It In addition, FIG. 14 shows that the linear velocity is 7.0 m / s, respectively.
When recorded with (a) m = n-1 and (b) m = n-2
Of jitter, α₁, Α_cIt is a contour map which shows dependence.
Pw, Pe, Pb and β used for measurement in each figure_mIn each figure
Shown above. At a linear velocity of 3.5 m / s, m = n
In both cases of −1 and m = n−2, α ₁= 0.7 ~
0.8, α_cIn the vicinity of = 0.35 to 0.40
Is it possible to obtain low jitter (approximately 7% or less)?
It At a linear velocity of 7.0 m / s, m = n-1, m = n
-In both cases, α ₁Around = 0.5, α_c= 0.
Around 40, the lowest jitter is obtained.
Recognize. Α in the neighborhood where the minimum jitter is obtained₁, Α_cAgainst
Then, in either case, Σα_iSatisfies the condition of <0.5n
Add In this embodiment, the linear velocity is 3.5 m / s and 7.0.
In either case of m / s, by setting m = n-2,
A lower jitter value is obtained, and when m = n-1
Large α compared to₁Low jitter is obtained
There is.

Furthermore, the medium of Example 1 was changed to NA =
Using a 0.63 evaluator, the recording pulse division method was changed as shown in Table 2 to evaluate the linear velocity dependence of jitter.
The reference clock period T is inversely proportional to the linear velocity.
The pulse division method is m = n-1, α _i + β _i-1 = 1.0
(2 ≦ i ≦ m) and α _i = α _c = constant (2 ≦ i ≦ m). Pw, Pb, and Pe were constant regardless of the linear velocity.
Here, in the pulse division method of Table-2, Σα _i <0.5n is satisfied at all linear velocities. Good overwrite characteristics were obtained from the standard linear velocity of DVD to about 1 × to 2.5 ×. This medium shows good overwrite characteristics in 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 On the substrate, a lower protective layer (Zn
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. The film thickness of each layer is shown in Table-3. All thin films were formed by the sputtering method without releasing the vacuum. The reflective layer was formed at an ultimate vacuum of 2 × 10 ⁻⁴ Pa or less, an Ar pressure of 0.54 Pa, and a film forming rate of 1.3 nm / sec. Its volume resistivity is 5
The area resistivity was 5 nΩ · m and 0.28 Ω / □. Impurities such as oxygen and nitrogen are below the detection sensitivity in X-ray excited photoelectron spectroscopy, and it can be considered that the total amount is less than about 1 atomic%. The film density of the (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer is 3.
50 g / cm ³ , theoretical bulk density 3.72 g / cm
It was 94% of ³ . The recording layer density was 90% of the bulk density. The thermal conductivity of the protective layer estimated from thermal simulation is 3.5 × 10 ⁻⁴ pJ / (μm · K · n
sec).

Recording (overwriting) is performed on the medium thus created by using the pulse division method shown in FIG. 10A for each layer structure of each medium at 1 × speed and 2 × speed respectively. went. After that, first time, 10
Times, the jitter after overwriting 1000 times was measured.
For measurement, both recording and reproduction, wavelength 637 nm, NA =
An optical system of 0.63 was used. Table 3 summarizes the optimum pulse division method, jitter, Rtop, and modulation degree at 1 × speed for each medium.

[0184]

[Table 3]

In both cases, the minimum mark length is 0.4 at 1 × speed.
The mark length modulation recording of μm can be performed, and a large initial modulation degree is 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%. The thickness of the upper protective layer 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 after 1000 times of overwriting, the jitter is 10 to 12%.
When the thickness of the upper protective layer is 40 nm, the initial jitter is 13
% Or more, and it was rapidly deteriorated due to repeated overwriting to 20% or more. Furthermore, the recording layer thickness is set to 30
In Example 2 (h2) having a large thickness of nm, the initial recording jitter was 13% or more, and the deterioration of the jitter due to repeated overwriting was remarkable. Example 2 (i2) in which the thickness of the lower protective layer was 45 nm had poor repeated overwrite durability. In addition, the thickness of the reflective layer is 250 nm is 200
A better jitter than that of nm was obtained. That is, it is understood that the "ultra-quenching structure" is preferable in such high density mark length recording.

Next, the recording power Pw dependency of the jitter of the medium of Example 2 (g1) was evaluated. The pulse division method is 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. After that, α ₁ and α _c = α _i (2
The dependency of jitter on <i <m) was evaluated. At double speed, α ₁ = 0.5, α _c = 0.4, β _m = β _n−1 = 0.
5, Pw = 14 mW, and at 1 × speed α ₁ = 0.7, α
_c = 0.3, β _m = β _n−1 = 0.5, and Pw = 14 mW. At this time, at double speed, Σα _i = 0.3n (n =
3), 0.33n (n = 4), 0.34n (n = 5),
It was 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
.About.14). The results are shown in FIG. Recording power Pw dependence of jitter after initial overwriting and 10 times overwriting, and reflectance Rto after overwriting 10 times
The recording power Pw dependence of p and modulation Mod is shown. (A) is for double speed recording, and (b) is for single speed recording. Note that Rtop corresponds to Itop in FIG. Further, in the figure, DOW (Direct Overwrite) means overwrite. Next, the overwrite durability was evaluated. The result is shown in FIG. Overwrite 1000 for jitter, reflectance and modulation
The values up to the next time are shown. (A) is for double speed recording, and (b) is for single speed recording. In either case, the jitter is
It gradually increased up to about 10 times, but became stable after 10 times, and the jitter, the degree of modulation, and the reflectance were hardly deteriorated up to 1000 times.

Further, Pw = 1 in the same pulse division method as in the above double speed (linear velocity 7 m / s) except that the medium has a linear velocity of 9 m / s and a reference clock period of 14.9 nsec.
Overwriting was performed at 4 mW. Elimination ratio is 30d
A sufficient value of B or more was obtained. Further, the jitter was also good at less than 11%. For the medium of Example 2 (g1), Pw = 14 m in the linear velocity range of 3 to 8 m / s.
W, Pb = 1 mW, Pe / Pw = 0.5, β _m = 0.5
A constant jitter was obtained, and good jitter was obtained by changing only α ₁ and α _c . 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.
Up to α ₁ = 0.65, α _c = 0.4, linear velocity 7-
Α ₁ = 0.55, α _c = 0.45 over 8 m / s,
If you change it in at least 3 steps,
A good jitter of less than% was obtained. Finer, 1m /
It is considered that better jitter can be obtained at each linear velocity by changing α ₁ and α _c in steps of s. 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 it exceeded mW, the jitter deteriorated sharply. Where Pe
When the 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) having an upper protective layer thickness of 20 nm and Example 2 (d2) having a thickness of 40 nm will be compared. The recording mark length dependency was measured for both media 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 was evaluated when the mark length was reduced from 0.5 μm. The recording linear velocity was constant at 3.5 m / s, the pulse division method was also constant as described above, and the reference clock period was changed to change the mark length. However, when the shortest mark length is 0.46 μm or more, the reproduction speed is 3.5 m / s due to the restrictions on the device.
Since it becomes difficult to control CLV, playback speed is 5m / s
And In addition, the shortest mark length 0.4 μm is for playback only D
It corresponds to the VD standard. The results are shown in FIG. (A)
Is the medium of Example 2 (g1), (b) is the medium of Example 2 (d2).
Is the medium of.

It is understood that the medium of Example 2 (g1) can be used with the shortest mark length of about 0.38 μm and the jitter of less than 13%. By using an optical system with NA = 0.63, it was possible to reduce the jitter by about 2%. Further, if the equalizer during reproduction was optimized, it was possible to reduce the jitter by about 2%. In addition to this, NA =
It is considered that if an optical system of 0.65 is used, sufficiently good jitter can be obtained even at 0.35 μm. Example 2 (d
In the medium of 2), the jitter with a mark length of 0.45 μm or more is almost satisfactory, but the jitter abruptly increases with a mark length of less than 0.45 μm, and the jitter is 13% or more at a mark length of 0.40 μm, which is unusable. It has become possible. Next, in order to evaluate a so-called tilt margin, after recording a random pattern signal modulated by EFM plus over a plurality of tracks on the medium of Example 2 (g1), the substrate was intentionally moved with respect to the optical axis of the reproduction laser beam. It was tilted and the change in jitter during playback was measured. The recording / reproducing optical system has NA = 0.6, and the recording linear velocity is 1 × or 2 ×, both of which are reproduction after overwriting 10 times. The measurement results are shown in FIG. 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 with no problem in a normal drive.

<Acceleration Test> An EFM plus modulated random pattern was recorded on a part of the tracks of the medium of Example 2 (g1) with Pw = 13 mW using the above optimum pulse division method, and the jitter was measured. . After that, this 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 only deteriorated by about 1% after 1000 hours. In addition, the acceleration test 10
After 00 hours, when a random pattern was recorded on another track under the same conditions as above and the jitter was measured, a deterioration of about 2% was observed, but at this level there is no practical problem. In addition, the same recording was performed at 1 × speed and 2 × speed, and 8
The modulation degree before and after the acceleration test for 1000 hours under high temperature and high humidity of 0 ° C./80% RH was evaluated. At 1 × speed, the initial modulation was 61% and the modulation after the acceleration test was 58%. At double speed, the initial modulation is 60% and the modulation after the acceleration test is 58%.
Met. <Stability Against Reproducing Light> The medium of Example 2 (g1) was irradiated with reproducing light at a power up to 1.2 mW.
It did not deteriorate at all for about 0 minutes. Next, power 1.0
The reproduction light was repeatedly irradiated up to 1,000,000 times at mW, but the increase in jitter was less than 2%.

(Example 3) The composition of the recording layer was changed to Ge _0.05 Sb.
_A medium was prepared with the same layer structure as in Example 2 except that _0.71 Te _0.24 was used. The film thickness of each layer and the evaluation results are displayed.
4 shows. An optical system with NA = 0.63 was used for the measurement. Similar to Table-3, α ₁ , α _c , and
The jitter was evaluated by optimizing β _n-1 and setting Pw and Pe so that the jitter was also minimum. In each case, the mark length modulation recording with the shortest mark length of 0.4 μm can be performed at 1 × speed, and a large initial modulation degree is obtained. Example 3
Regarding (a), as in Example 2 (a1), good characteristics were obtained at recording linear velocities of 1 × and 2 ×, but 9 m / s.
Then, the jitter was higher by 1 to 2% than that in Example 2 (a1). In addition, Example 3 in which the thickness of the upper protective layer is 30 nm
In (a) to (f), a jitter of less than 10% was 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 was only greater than 13%.

[0192]

[Table 4]

(Embodiment 4) The layer structure is such that the lower protective layer (Zn
S) ₈₀ (SiO ₂ ) ₂₀ with a film thickness of 215 nm and a recording layer Ge
_0.05 Sb _0.69 Te _0.26 18 nm, upper protective layer (Zn
S) ₈₀ (SiO ₂ ) ₂₀ 18 nm, reflective layer Al _0.995 T
a _0.005 was set to 200 nm. This recording layer composition has a linear velocity of 3
Good characteristics can be obtained by recording at up to 5 m / s, which is what is called 1 × speed. However, since the amount of excess Sb is slightly smaller than that of Examples 2 and 3, it is excellent in stability over time, and is preferable for importance of storage stability of recorded information and deterioration due to repeated reproduction, that is, reproduction light durability. . The following was evaluated by an optical system with NA = 0.6. The optimum pulse division method was determined as follows. Recording linear velocity 3.5m /
s, Pw = 13 mW and Pe / Pw = 0.5, and in FIG. 10, β _m = 0.5 and α ₁ and α are constant.
_A pulse division method was selected in which _c was varied to obtain the minimum jitter. FIG. 19 shows the α ₁ and α _c dependence of the jitter after overwriting 10 times as a contour map of the jitter. Since 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 that, α ₁ = 0.6, α _c = We chose 0.35. 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). Degree of modulation 65%, playback only D
The value was comparable to that of VD. Rtop is 23%
Although it is only about 15%, if it is actually 15% or more, it is considered that reproduction can be performed even with the existing reproduction-only drive. Therefore, Pw = 12.5 mW and linear velocity 3.5 in the recording medium of the present invention.
Commercially available read-only DVD that records image data at m / s
When I tried to play it on the player, the focus servo,
Tracking servo signal and jitter are normal playback-only DV
A characteristic equivalent to that of D was obtained.

<Repetition Overwrite Durability> FIG. 20
, Pw = 12.5 mW, jitter, Rtop,
The dependence of the modulation factor on the number of repeated overwrites is shown. 1
It shows sufficiently stable characteristics even after overwriting 000 times.

<Acceleration Test> On some tracks of this medium,
Using Pw = 13 mW, the optimum pulse division method was used to record an EFM plus modulated random pattern and measure the jitter. After that, the medium is heated to 80 ° C /
An accelerated 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, the deterioration was less than 0.5% after 1000 hours. In addition, the degree of modulation is 65% at the beginning
Which was 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.
Although the deterioration was about 10%, there is no problem in practical use at this level.

<Stability Against Reproducing Light> This medium was irradiated with reproducing light at a power up to 1.3 mW, but no deterioration occurred in about 10 minutes. Next, the power is 1.0mW
As a result, the reproduction light was repeatedly irradiated up to 1 million times, but the increase in jitter was less than 1%.

Example 5 In the layer structure of Example 2 (a1), the recording layer was made of Ge _0.05 Sb _0.75 Te _0.20 . The evaluation was performed using an optical system with NA = 0.6. α ₁ = 0.4, α _c
= 0.3, β _m = 0.5, Pw = 14 mW, Pe / Pw
The best jitter was obtained at = 0.5. The initial modulation was also large enough. After 10 times of overwriting, the jitter was barely 10%, and remained less than 13% even after 1000 times.

<Acceleration Test> On some tracks of this medium,
Using Pw = 14 mW, the optimum pulse division method was used to record an EFM-plus-modulated random pattern and measure the jitter. After that, the medium is heated to 80 ° C /
An accelerated test was performed under high temperature and high humidity of 80% RH. When the jitter of this track was measured again after 500 hours from the acceleration test, it was only deteriorated by about 2%. Also, 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 and found to be 3%.
Although the degree of deterioration was observed, there is no problem in practical use at this level.

<Stability to reproducing light> This medium was irradiated with reproducing light at a power up to 1.0 mW, but no deterioration was observed in about 10 minutes. Next, the power is 1.0mW
As a result, the reproduction light was repeatedly irradiated up to 1 million times, but the increase in jitter was less than 3% and less than 13% was maintained.

Example 6 In the layer structure of Example 4,
The recording layer was made of Ag _0.05 Ge _0.05 Sb _0.67 Te _0.23 . N
Evaluation was performed using an optical system with A = 0.6. At a linear velocity of 3.5 m / s, the dependence of jitter on the pulse division method (α ₁ and α _c ) is Pw = 13 mW, Pe / Pw = 0.5, m = n
When measured at -1, β _m = 0.5, the contour map 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).

In FIG. 21 (b), first time, 10 times, 1000
Figure 21 shows the power dependence of jitter after overwriting
(C) shows the power dependence of Rtop and the modulation degree after 10 times of overwriting. Good jitter was maintained in a wide recording power range after overwriting 1000 times, and Rtop of 18% and modulation of 60% or more were achieved. FIG. 22 shows the changes in jitter, Rtop, and the modulation degree after overwriting 10,000 times at Pw = 13 mW. There was no deterioration except that the jitter increased by about 1% in the initial stage. Further, the result of measuring the shortest mark length dependency of the jitter in the same manner as in Example 1 is shown in FIG.
3 shows. Minimum mark length of 0.38 μm and jitter of 10%
It was very good with less than. For this medium, m
When the pulse division method with = n-2 was also evaluated, the same characteristics as in FIG. 21 were obtained at α ₁ = 1.0, α _c = 0.5, and β _m = 0.5. Σα _i with n = 3
= 0.48n, n = 4, Σα _i = 0.48n, and n ≧ 5, Σα _i = 0.46n to 0.47n.

(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 the pulse division method dependence of the jitter was evaluated with w = 0.5 and β _m = 0.5, the contour diagram shown in FIG. 24A was obtained. The optimum values are α ₁ = 1.0 and α _c = 0.5, and in this case, Σα _i was constant at 0.5n regardless of n. The recording power dependence and the repetitive overwrite characteristics up to 1000 times are shown in FIGS. 24 (b) and 24 (c). The jitter and power margin of the first recording were better than those of Example 5, but the deterioration was caused by repeated overwriting, and after 1000 times, the jitter was rather worse. When the reproducing light power was further increased to 1 mW, 5
In about a minute, the jitter deteriorated and increased to over 10%. This difference cannot be explained by the recording sensitivity difference of 0.5 to 1 mW. The main cause of reproduction light deterioration is that the temperature rises to about 50 to 100 ° C., and it is understood that the addition of Ge 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 with 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
It was set to 00 nm. At the time of recording, based on the pulse division method shown in FIG. 10A, fine adjustment was performed so as to obtain the best jitter 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, which is constant, and a strategy in which β _m = 1.0 is obtained, almost the best jitter is obtained. Also, Pw = 1
3 mW, Pe / Pw = 0.4 (Pe = 5 mW), Pb =
The optimum recording power is 2.0 mW, and Pb / Pe = 0.
This is because the recording layer of this comparative example needs to maintain the TL in FIG. 9 at a relatively high value. Even if Pb is less than 1 mW, the jitter is bad,
Even when Pb was 3 mW or more, the jitter was deteriorated. Based on this pulse division method, a precise pulse width adjustment of about 0.02 was performed for α ₀ according to the mark length, and the mark length dependency was measured as in Example 2. The results are shown in Fig. 26 (a). Also, the linear velocity dependence during overwriting was measured. The results are shown in Fig. 26 (b). Regarding the linear velocity dependence, the reference clock period was changed according to the linear velocity so that the shortest mark length was 0.4 μm, and the reproduction was always performed at 3.5 m / s. Regarding the linear velocity dependence,
The jitter after overwriting 10 times and the jitter after overwriting once after DC erasing are shown. As shown in FIG. 26A, the jitter was 10% at the shortest mark length of 0.4 μm, and the jitter was abruptly deteriorated when the length became shorter. Further, as shown in FIG. 26B, the jitter is worse at a recording linear velocity of 5 m / s or more. However, the jitter is 2 to 3% in the recording after the DC erasing.
It has fallen over. From this, due to the non-uniform temperature rise due to the difference in absorption coefficient between the so-called crystalline state and amorphous state,
It is considered that the erasing failure or the distortion of the shape of the amorphous mark occurs and the jitter is deteriorated.

The jitter after overwriting was 20% or more at a linear velocity of 7 m / s, but was about 15% in the recording after DC erasing. Therefore, it is considered that the high jitter at high linear velocity is not due to the selection of an appropriate pulse division method. This recording layer has high jitter due to coarse grains, but in addition to this, at a linear velocity of 5 m / s or more, the previous mark was not sufficiently erased at the time of overwriting, and the jitter after recording the DC was erased. The effect is clearly visible as a difference. In addition,
The difference in jitter between the case where the medium of Example 2 (g1) was overwritten at 7 m / s and the case where recording was performed after DC erasing 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 more, recording after DC erasing has no problem as described above, but jitter is deteriorated during overwriting. Therefore, in order to reduce the jitter, it is necessary to add a light absorbing layer or the like to correct the absorptance.

(Comparative Example 4) In Example 2 (g1), the recording layer was made of Ge _0.15 Sb _0.64 Te _0.21 . Initial crystallization was extremely difficult, and the initialization was finally performed by irradiating the initialization beam a plurality of times, and the jitter was measured by overwriting, but no matter how the pulse division method was changed within the range of FIG. % Or less jitter was not obtained. Further, when overwriting was repeated, the jitter increased by several% between 10 and 100 times.

Comparative Example 5 In the layer structure 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 =
The best jitter was obtained at 0.5, Pw = 14 mW, and Pe / Pw = 0.5, but the jitter was barely over 11% after overwriting 10 times, and 13% or more after 1000 times. Has become.

<Acceleration test> On some tracks of this medium,
Using Pw = 14 mW, the optimum pulse division method was used to record an EFM-plus-modulated random pattern and measure the jitter. After that, the medium is heated to 80 ° C /
An accelerated test was performed under high temperature and high humidity of 80% RH. When the jitter of this track was measured again after 500 hours from the acceleration test, it deteriorated by about 3% to 13% or more. 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, a deterioration of about 5% was observed and the deterioration was rapid.

<Stability Against Reproducing Light> When the reproducing light was irradiated to the medium at an increased power of 1.0 mW, it was 1
After 0 minutes, the jitter increased by 3% and was very unstable.
In addition, the degree of modulation was lowered and the marks tended to disappear.

(Embodiment 7) With respect to the medium of Embodiment 2 (a1), the speed from 1x speed (3.5 m / s linear velocity, reference clock period T = 38.2 nsec) to 2.25x 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 E is inversely proportional to the linear velocity.
A positive signal was recorded. Further, to determine the _{α i + β i-1 =} 1.0 constant at beta _i. It should be noted that only the final off-pulse section β _m was changed to be longer as the linear velocity was slower. In such a pulse division method, in the explanatory diagram of the gate generation timing in FIG. 11, the reference clock cycle T
(A constant delay may be added), and _one fixed-length pulse with τ ₁ = 19 nsec (Gat
e1) and n-2 fixed-length pulses (Gate2) of τ _c = 11 nsec may be generated, and only Gate3 that determines the final off-pulse length may be changed according to the linear velocity, and the pulse generation circuit is simplified. It is possible and preferable. Furthermore, 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, Σα _i <0.47 n is satisfied, and thus thermal damage is sufficiently suppressed. Table-5 shows
The values of jitter when β _m was changed at each linear velocity were summarized. In the table, v represents 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 in the case where the pulse division method is more flexibly variable as in the second embodiment, but a value of less than about 10% is obtained from 1 × speed to 2.25 × speed. Has been. Where β ^H _m = 0.3,1 at double speed
At double speed, β ^L _m = 0.6 (point surrounded by a square), β
It can be seen that if _m is changed in inverse proportion to the linear velocity, jitter of less than 10% can be obtained at each linear velocity from 1 × to 2 ×. Further, in this embodiment, although the margin of β _m is small, even if β _m = 0.2 is kept constant, a jitter of less than 10% can be obtained from 1 × speed to 2.25 × speed. In this way, it is possible to simplify the pulse generation circuit that can be changed according to the linear velocity. In addition, Pb, P may be previously recorded on the recording medium by an uneven pit or a modulated groove meandering signal.
By describing e / Pw, Pw, τ ₀ , τ _c , and (β ^L _m , β ^H _m ), the optimum recording condition can be automatically determined according to the linear velocity at the time of overwriting.

[0210]

[Table 5]

(Embodiment 8) The layer structure is changed to the lower protective layer (Zn
S) ₈₀ (SiO ₂ ) ₂₀ with a film 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 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 minimum mark length (3T mark length) is changed from 0.4 μm to 0.25 μ by changing the reference clock period T to 0.5 mW.
Recording was carried out by changing to m. When the mark length of the 3T mark is 0.4 μm, T = 38.2 nsec, 0.2 μ
When m, T = 19.1 nsec. The recording laser wavelength is 637 nm and NA = 0.63. Since this focused laser beam has a Gaussian distribution, it can be recorded at a high density higher than the optical resolution by utilizing only the high temperature part of the central part. Recorded part is wavelength 432n
m, NA = 0.6, and power was 0.5 mW for reproduction with a blue laser beam. This laser light is generated by a non-linear optical effect from laser light having a wavelength of about 860 nm. With this layer structure, the modulation degree is 5 even at 432 nm.
A large degree of modulation of 0% or more was obtained. Furthermore, FIG.
8 shows the jitter as the shortest mark length dependency when the reproduction was performed by the optical system of 637 nm and NA = 0.63 used for recording and when the reproduction was performed by the optical system of 432 nm and NA = 0.63. In measurement, the equalizer settings are optimized as much as possible at each measurement point. With this recording medium, the shortest mark length is 0.3μ when reproducing blue laser light.
It can be seen that even with m, a good jitter of less than 13% was obtained.

Comparative Example 6 In the layer structure of Example 2 (a1), the recording layer was 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 fixed at 4.5 mW, only Pw was changed and overwrite recording was performed up to the 10th time. The recording power dependence of the jitter at this time is shown in FIG.
In the figure, 1 write is the first recording of an unrecorded disc,
1DOW means the first overwrite, and 10DOW means the 10th overwrite. Next, Pw = 8.
Overwrite recording was performed up to the 10th time by changing only Pe while keeping constant at 5 mW. FIG. 27B shows the erase power dependence of the jitter at this time. In any case, good jitter was obtained in the first recording (1 write), but the jitter deteriorated sharply when overwriting was performed even once. It is considered that the recording layer composition in this comparative example is Te-rich composition as compared with the line A in FIG. To be

(Example 9 and Comparative Example 7) Example 2 (a)
In the layer structure of 1), the recording layer composition was changed as shown in Table-6. Ge _0.05 Sb _0.73 Te _{0.22 The} amount of Ge was changed by co-sputtering a 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, α ₁ , α _c , Pw, and Pe were changed, and a condition for minimizing the jitter after 10 times of overwriting was searched for. The minimum jitter obtained for each recording layer composition is shown in Table-6. Jitter increased as the amount of Ge added increased, and when Ge was 10 atomic% or more, the jitter at double speed became very high, 14%. It should be noted that this medium is at 80 ° C and 80% R
When an accelerated test was performed under the condition of H, Example 9 (a)
Examples 9 (b) and (c) were slightly better than those of Comparative Example 1. That is, when the signal recorded before the acceleration test was read out after 2000 hours of the acceleration test, Example 9 (a) to
In either case of (c), the jitter was only worsened by about 1%. Moreover, Example 9 (a)-
The initial degree of modulation of (c) was 61 to 63%, and the degree of modulation of 58 to 59% was obtained even after the acceleration test for 2000 hours. The reflectance was almost unchanged. Particularly, 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, the best jitter was obtained when 1 to 2 atomic% of Ta was added to GeSbTe.

Example 10 and Comparative Example 8 Example 2 (g
In the layer structure of 1), the recording layer is GeS with In added.
bTe. In is a GeSbTe target with InS
bTe was added by co-sputtering. The composition of each recording layer is Ge _0.05 Sb _0.74 T in Example 10 (a).
e _0.21 , Example 10 (b) is In _0.023 Ge _0.048 Sb
_0.719 Te _0.21 , Example 10 (c) is 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. The result of evaluating the power dependence of the jitter of each medium is shown in FIG.
It is shown in (b), (c) and (d). Recording speed is 3.5m in the upper row
In the case of / s, the lower row shows the case of 7.0 m / s. The optical systems used were 637 nm and NA =. 63.
When the linear velocity is 3.5 m / s, α ₁ = 0.6, α _c = 0.3
5, β _m = 0.5, and in case of 7.0 m / s, α ₁ =
0.4, α _c = 0.4 and β _m = 0.5. Pb =
It was fixed at 0.5 mW. Pe was fixed at two values, and only Pw was changed to measure the Pw dependence of jitter. The Pw margin was significantly improved by adding the In amount of about 2 to 5 atomic%. However, when it exceeded 10 atomic%, the jitter was worse than when it was not added. In addition, the jitter after 1000 times of overwriting is as shown 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 under an environment of 80 ° C./80% RH. The accelerated test was carried out 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 of 57% was obtained even after the 2000-hour acceleration test. The reflectance was almost unchanged. The deterioration of jitter was about 3% when recording was newly performed on the unrecorded area after 2000 hours, but this is at a level that causes no practical problems.

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

[0219]

[Table 7]

The wobble modulation method is binary phase modulation in which the carrier wave period T _w is 32 times the reference data clock period T = 38.2 nanoseconds. Here, the phase modulation wobble is a phase shift of the wobble wave by π corresponding to 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 wave 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. Since the switching cycle T _d of digital data 0 and 1 is lower than T _w , and T _d is an integer fraction of T _w , the wobble waveform changes continuously even if the phase is shifted by π. ing. A preferable point of this modulation method is ATIP (Absolute T
Unlike the frequency (FM) modulation used for ime in Pregroove), the meandering frequency is constant and the period is modulated at a high frequency of 32T. Therefore, the wobble clock is referenced to establish the rotation synchronization of the disk. At the same time, the data clock can be directly generated in synchronization with the wobble clock. In order to change the phase by modulating digital data in this way, a ring modulator as shown in FIG. 31, for example, is used. Digital data is applied with positive and negative voltages ± V corresponding to 0 and 1. At the time of forming the stamper master, laser light for photoresist exposure is exposed while meandering in the radial direction according to a wobble waveform that is binary-phase modulated between voltages of ± V _w . At this time, the exposure beam can be made to meander by applying the ring modulator output wave to the EO modulator.

A little more detail will be described below. 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
Since it is guided to the lower side of the output side transformer via ₂ , the modulation is inverted at the output terminal by -V _w · cos (2π
f _c t) to become.

On the other hand, at the output of the input side transformer, -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 wave that has passed 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 thus modulated is input to the EO modulator, and the exposure beam can be made to meander. In this embodiment, all wobble amplitudes are 60 nm (peak-
to-peak value). In the case of a medium in which recording is performed only in the groove, the lower limit of the preferred groove depth is λ / (20n) = 20. 5 nm, the upper limit is λ / (10
n) = 40.8 nm. Wavelength 6 is required to evaluate this medium.
An optical system with 37 nm and NA = 0.63 was used.

As in the second embodiment, m = n-1, α _i + β
_i-1 = 1.0 (2≤i≤m), α _i = α _c = constant (2≤i
i ≦ m), the linear velocity is 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, and 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 modulation factor were measured. Also, 3.5 m / 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, in Example 11 (k), the depth was 18 nm.
Although it has a very shallow groove, the push-pull signal was hardly detected and tracking servo could not be applied. Further, it is very difficult to form such a shallow groove even in forming the stamper, and in practice, a very large unevenness is observed in the tracking servo signal. FIGS. 32A and 32B show the groove shape dependence of the modulation degree and Rtop. Examples 11 (h) to 11 (j) have a groove with a depth of 42 nm, but the reflectance is significantly lower than that with a depth of 27 nm, which is 5% or more, which is not preferable. The modulation degree decreases particularly when the groove is thin, and when the width is 0.23 μm,
Even at the depth of 35 nm, the degree of modulation was significantly reduced. In this embodiment, the layer structure is the same, but if the depth is 42 nm, if the layer structure with high reflectance is used to compensate for the decrease in reflectance, the decrease in modulation degree becomes more remarkable. That is, the groove having a depth of 42 nm is not suitable for recording in the groove. Groove depth 4
At 0 nm or more, the wobble signal remarkably 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, the jitter is deteriorated by 1 to 2% or more at the linear velocity of 3.5 m / s, and is 2 to 3% at the 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
_0.05 Sb _0.73 Te _0.22 16 nm, upper protective layer (Zn
S) ₈₀ (SiO ₂ ) _{20 20} nm, the first reflective layer Al
_The film thickness of _0.995 Ta _0.005 was 40 nm, and the film thickness of the second reflective layer Ag was 70 nm. The lower protective layer to the first reflective layer are formed by the sputtering method without releasing the vacuum. After the first reflective layer is formed, it is exposed to the atmosphere and left for several minutes, and then the second reflective layer is formed again by the vacuum method by the sputtering method. A film was formed. After forming the second reflective layer, a UV-curable resin was laminated by spin coating to a thickness of 4 μm as an overcoat layer. The two discs thus produced were laminated so that the overcoat layers face each other. The film formation of the first reflective layer was performed 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 are below the detection sensitivity in X-ray excited photoelectron spectroscopy, and it can be considered that the total is less than about 1 atomic%. The film formation of the second reflective layer has an ultimate vacuum of 4 × 10 ^−4.
Pa was performed at a pressure of 0.35 Pa or less. The volume resistivity was 32 nΩ · m. Impurities such as oxygen and nitrogen are below the detection sensitivity in X-ray excited photoelectron spectroscopy, and the total is almost 1
It could be considered to be less than atomic%. Wavelength 637nm, NA
Using an optical system of 0.60, linear velocity 3.5 m / s, α ₁
= 0.4, α _c = 0.35, β _m = 0.5, the jitter was measured after overwriting 10 times. Pw = 11 mW, Pe = 6.0 mW, Pb
= 0.5 mW, the minimum jitter of 6.5% was obtained. When this medium was left under high temperature and high humidity of 80 ° C. and 80% RH for 500 hours and then recorded in the same manner, no deterioration was observed at all.

(Embodiment 13) A stamper having spiral grooves with wobbles having a groove pitch of 0.74 μm, a groove width of 0.3 μm and a groove depth of 40 nm was formed, and based on this,
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, 36mm from radius 22.5mm to 58.5mm
As a recording area, and the recording area was 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 the 191th track, each band width is exactly 36.
It is not / 255. Therefore, the outermost end of the recording area is 58.54 mm. The channel bit length is 0.
The reference clock is 26.16 MHz (T = 38.23 nsec) at a linear velocity of 3.49 m / s. 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 in the center radius of each band and the total number of wobbles 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 the number of wobbles is constant with an accuracy of 1%. That is, the ZCAV system can perform recording with a constant linear density, which is not different from the CLV system, and sufficiently satisfies the standard for read-only DVD. Based on the above premise, when the disc is rotated so that a linear velocity of 3.49 m / s is obtained at each band center radius, the wobble period is exactly the reference clock period T = 38.23 nse of DVD data.
9 times as large as 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 reproduced from the wobble of each band during the CAV rotation is multiplied by 1/9 to generate the data reference clock T _q in each band, and the EFM is performed based on the clock.
Record positively modulated data. When reproducing, if the rotation synchronization is achieved so that the data reference clock frequency generated from the recorded data becomes 26.16 MHz, the variation of the channel bit length in each zone is less than ± 1%. Therefore, the reproduction in the CLV mode can be substantially performed 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 (PhaseLocked Loop) is used so that they are synchronized. The rotation speed is finely adjusted by the control method. The rotation control by such PLL control is currently performed in the reproduction of the DVD-ROM, 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 reflective layer was 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, and Table-3
Jitter measurement was performed using the optimum pulse division method in FIG. Film thickness 3
The best jitter of 12% was obtained at around 00 nm. Even if the reflective layer was thicker or thinner than that, even 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 405nm, NA = 0.6
Using the optical system of No. 5, it is almost circular and the spot diameter is about 0.5μ.
A beam of m (diameter at 1 / e ² intensity of Gaussian beam) was generated, and recording / reproduction was performed through a substrate having a thickness of 0.6 mm. An EFM plus modulation signal was recorded at a linear velocity of 4.86 m / s with the length of the shortest mark (3T mark) being 0.25 μm. With 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 and Pe = 4.0 mW, the jitter was 10%. It was found that recording / reproducing with a blue laser enables higher quality recording than in the case of Example 7. Further, even a medium designed for the current red laser can be recorded / reproduced by the blue laser as it is to achieve high density.

(Example 16) Layer structure of Example 2 (a1)
In, the recording layer is Ga_0.05Ge_0.05Sb_0.68Te _0.22
Was prepared. Initialization is the same as in Example 2 (a1)
I went. For measurement, wavelength 637 nm, NA = 0.6
The optical system of 3 was used. The length of the shortest mark 3T is 0.4μ
The EFM plus modulation signal with m is set to a linear velocity of 3.5 m / s.
I went there. With the same recording pulse strategy as in the second embodiment
m = n-1, α_i+ Β_i-1= 1.0 (2 ≦ i ≦ m), α
_i= Α_c= Constant (2 ≦ i ≦ m), and α₁= 0.5, α
_c= 0.3, β_m= 0.5, Pw = 13.5 mW,
With Pe = 6.0 mW and Pb = 0.5 mW, the overlap
Characteristics were evaluated. First recording (non-overwrite),
10 overwrites, 100 overwrites, 10
After overwriting 00 times, the jitter is 6.9%,
6.7%, 7.0% and 7.3% were good. Furthermore
Similarly, at a linear velocity of 7.0 m / s,₁= 0.4, α_c
= 0.35, β_m= 0.5, Pw = 14.0 mW,
With Pe = 7.0 mW and Pb = 0.5 mW,
Characteristics were evaluated. First recording (non-overwrite),
10 overwrites, 100 overwrites, 10
Overwriting by 00 times, each jitter is 7.4%,
7.7%, 8.0%, and 8.5% were good. Modulation degree
In all cases, a value of 55 to 60% was obtained. This medium is 80
Leave for 1000 hours in an accelerated test environment of ℃ / 80% RH
I recorded it before the test. Recorded before accelerated test
The deterioration of the signal jitter was less than 1%. Also the modulation
A value of 52 to 57% was obtained.

(Embodiment 17) As in Embodiment 2, 0.6
Pitch 0.74 on mm thick polycarbonate resin substrate
A wobble groove of μm is formed, and reflection is performed as shown in FIG.
The layer, the second protective layer, the recording layer, and the first protective layer were formed in this order.
Reflective layer Al_0.995Ta_0.005Is a film thickness of 165 nm,
Protective layer (ZnS)₈₀(SiO₂)₂₀Is a film thickness of 20 nm, recording
Layer In_0.03Ge_0.05Sb_0.70Te_0.22With a film thickness of 16 nm,
First protective layer (ZnS)₈₀(SiO₂)₂₀A film thickness of 68n
m, respectively, was formed by a sputtering method. Of that
Then, facing the first protective layer, a glass plate having a thickness of 0.6 mm
Was in close contact. Initialization is performed via a glass substrate at 500
Irradiate with a laser beam of about mW at a linear velocity of 5 m / s.
It was Through this glass substrate, wavelength 637 nm, NA =
The recording layer is irradiated with laser light using an optical system of 0.6.
Recorded and played back. 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
With the same recording pulse strategy, m = n−1, α_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.
It was After overwriting 10 times, the jitter is 10.5%,
The degree of modulation was 61%. Furthermore, linear velocity 7.0 m / s
Similarly, in 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.
It was After overwriting 10 times, the jitter is 11.2%,
The degree of modulation was 61%.

[0236]

According to the present invention, overwriting can be performed at high speed, high-density mark length modulation recording with small mark edge jitter can be performed, and the stability of formed marks with time is extremely high. A very good optical information recording medium can be obtained. Further, by selecting an appropriate recording layer composition and layer structure, it is possible to obtain a phase change type optical recording medium having excellent reproduction compatibility with a reproduction-only medium and high repetitive overwrite durability. More specifically, it has reproduction compatibility with a so-called DVD disc, and can perform 1-beam overwriting in a wide linear velocity range including a standard reproduction 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 disc and show no deterioration even after overwriting ten thousand times or more. Further, since the medium of the present invention has a wide linear velocity margin, C
Even when recording is performed by rotating the medium at a constant angular velocity such as the AV method and the ZCAV method, it is possible to overcome the problem of the recording characteristic difference due to the linear velocity difference 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 shortened.

[Brief description of drawings]

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

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

FIG. 3 is a GeS showing a composition range of a recording layer of the medium of the present invention.
bTe ternary state diagram.

FIG. 4 GeSb showing the range of conventional GeSbTe composition
Te ternary state diagram.

FIG. 5 is a schematic diagram showing an example of the layer structure of the medium of the present invention.

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

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

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

FIG. 9 is a schematic diagram for explaining the 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.
The conceptual diagram explaining the timing of 3 types of gate generation circuits.

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

FIG. 13 is a graph showing the dependence of jitter on the recording pulse division method in Example 1.

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 degree in Example 2.

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

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

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

FIG. 19 is a graph showing the α ₁ and α _c dependence of the jitter after overwriting 10 times in Example 4.

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

FIG. 21A is a pulse division method dependency of jitter in Example 6, and FIG. 21B is a writing power dependency of jitter.
And (c) a graph showing the write power dependence of Rtop and modulation degree after 10 overwrites.

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

FIG. 23 is a graph showing the dependence of jitter on mark length in Example 6;

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

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 dependence of jitter on mark length and linear velocity in Comparative Example 3. FIG.

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

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

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

FIG. 30 is a diagram illustrating a relationship between a digital data signal and a wobble waveform.

FIG. 31 is a diagram illustrating a mechanism for modulating a wobble waveform with a digital data signal.

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

Continuation of the front page (56) Reference JP-A-5-282704 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 7/24

Claims (59)

(57) [Claims] To 1. A substrate, in order from the incident direction of the recording light, the first protective layer, a phase change type recording layer, the second protective layer, reflecting layer, the provided result, the crystal portion of the recording layer Not A recording medium is an optical information recording medium for recording information with a plurality of recording mark lengths of a shortest mark length of 0.5 μm or less in a recording / erasing state, an amorphous portion in a recording state, and a phase change recording layer When the film thickness is 5 nm or more and 25 nm or less, G
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 region surrounded by four straight lines B, 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 (however, the boundary A medium for optical information recording, comprising a thin film containing GeSbTe alloy as a main component having a composition (not including lines), and the second protective layer having a film thickness of 5 nm or more and 30 nm or less. 2. The GeSbTe ternary diagram wherein the recording layer is a straight line A connecting (Sb _0.7 Te _0.3 ) and Ge, and a straight line _B'connecting (Ge _0.03 Sb _0.68 Te _0.29 ) and (Sb _0.9 Ge _0.1 ). A region surrounded by four straight lines, 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 (but not including the boundary line) The optical information recording medium according to claim 1 , which is composed of a thin film containing a GeSbTe alloy as a main component having the composition described above. 3. A recording _{layer, Ge x (Sb y Te 1} -y) film on the basis of _1-x alloy (0.04 ≦ x <0.10,0.
72 ≦ y <0.8), The optical information recording medium according to claim 1 or 2 . 4. A recording _{layer, Ge x (Sb y Te 1} -y) film on the basis of _1-x alloy (0.045 ≦ x ≦ 0.075,
0.74 ≦ y consisting <0.8) according to claim 1乃 Itaru 3 Noise
The optical information recording medium according to any Re. 5. The recording layer further comprises O, N, and S.
5. The optical information recording medium according to claim 1 , which contains at least one element selected from the group consisting of 0.1 atom% or more and 5 atom% or less. 6. The recording layer further comprises V, Nb, and T.
containing at least one element selected from a, Cr, Co, Pt, and Zr, 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. Is
The optical information recording medium according to claim 1 . 7. The recording layer further contains at least one element selected from Al, In, and Ga, and the total content of these elements is 8 atomic% or less, and these elements and Ge are combined. The total content is 15 atomic% or less
The optical information recording medium according to claim 1 . 8. The recording layer has a film thickness of 10 nm or more and 20 nm or more.
The optical information recording medium according to any one of claims 1 to 7, which is as follows. 9. The second protective layer has a thickness of 10 nm or more and 25.
The optical information recording medium according to any one of claims 1 to 8, which has a thickness of nm or less. 10. A medium for recording or reproducing is incident information recording reproducing light through the substrate, any one of claims 1 to 9 first protective layer is a film thickness of 50nm or more <br / The optical information recording medium described in <>. 11. The reflective layer has a thickness of 40 nm or more and 300 or more.
nm or less and volume resistivity of 20 nΩ · m or more and 150 nΩ
The optical information recording medium according to any one of claims 1 to 10, having a size of m or less. 12. The reflective layer has a film thickness of 150 nm or more and 30 or more.
Below 0 nm, Ta, Ti, Co, Cr, Si, Sc,
A containing at least 0.2 atomic% and 2 atomic% of at least one of Hf, Pd, Pt, Mg, Zr, Mo and Mn
The optical information recording medium according to claim 11 , which is made of an 1-alloy. 13. The reflective layer has a thickness of 40 nm or more and 150.
nm, Ti, V, Ta, Nb, W, Co, Cr,
Si, Ge, Sn, Sc, Hf, Pd, Rh, Au, P
It is made of an Ag alloy containing at least one of t, Mg, Zr, Mo and Mn in an amount of 0.2 atomic% or more and 5 atomic% or less
The optical information recording medium according to claim 11 . 14. The reflective layer is a multilayer reflective layer composed of a plurality of metal films, and 50% or more of the total thickness of the multilayer reflective layer has a volume resistivity of 20 nΩ · m or more and 150 nΩ · m or less.
The optical information recording medium according to any one of claims 11 to 13 . 15. A film thickness of 5 n is provided between the second protective layer and the reflective layer.
11 through claim provided 100nm or less of the interface layer above m
15. The optical information recording medium according to any one of 14 . 16. A film thickness of 1 n is provided between the second protective layer and the reflective layer.
An interface layer of m or more and 100 nm or less is provided, and the interface layer is Ta, Ti, Co, Cr, Si, Sc, H.
An Al alloy containing at least one of f, Pd, Pt, Mg, Zr, Mo and Mn in an amount of 0.2 atomic% or more and 2 atomic% or less, and the reflective layer includes Ti, V, Ta, Nb, W. , Co, Cr, S
i, Ge, Sn, Sc, Hf, Pd, Rh, Au, P
The optical information recording medium according to claim 11 , comprising an Ag alloy or Ag containing at least one of t, Mg, Zr, Mo and Mn in an amount of 0.2 atomic% or more and 5 atomic% or less. 17. The Al layer between the interface layer and the reflective layer.
A layer of oxide of the alloy and / or Ag alloy is present,
Claims thickness of the oxide layer is 1nm or more 10nm or less
Item 16. The optical information recording medium according to item 16 . 18. The optical information recording medium according to claim 1 , wherein the tracks for recording information have a pitch of 0.8 μm or less. 19. A medium for recording information using only the groove as a track, the groove having a pitch of 0.8 μm or less on the substrate, the reproduction light wavelength of λ, and the refractive index of the substrate at that wavelength. The optical information recording medium according to claim 18 , wherein the groove depth is in the range of λ / (20n) to λ / (10n), where n is n. 20. For recording / reproducing data, light having a wavelength of 630 to 670 nm is focused on a recording layer through a substrate through an objective lens having a numerical aperture NA of 0.6 to 0.65. In the medium, the grooves have a groove pitch of 0.6 to 0.8 μm and a groove depth of 25.
˜40 nm, the groove width is 0.25 to 0.5 μm, and the groove has a meandering period of 30 to 40 times the reference clock period T of data, and the meandering amplitude (peak-to-p)
The optical information recording medium according to claim 19 , having an eak value of 40 to 80 nm. 21. A medium for recording information using tracks both in and between the grooves, the groove being formed on the substrate, the reproducing light wavelength being λ, and the refractive index of the substrate at that wavelength being n. When the groove depth is λ / (7n) to λ / (5n) or λ / (3.5n) to λ / (2.5n), both the groove width GW and the groove width LW are 0. 2μm or more 0.4μ
m or less and a GW / LW ratio of 0.8 or more and 1.2
The optical information recording medium according to claim 18 , which is as follows. 22. The optical information recording medium according to claim 1 , wherein an erasing power P capable of crystallizing an amorphous material is provided between recording marks.
When the recording light of e is irradiated and the time length of one recording mark is nT (T
Is a reference clock period, n is an integer of 2 or more), and the time length nT of the recording mark is expressed by 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 = n−k, and k is 0 ≦ k
≤2. Further, Σ _i (α _i + β _i ) + η ₁ + η ₂ = n, and η ₁ is η ₁
Real number ≧ 0, η ₂ is a real number η ₂ ≧ 0, 0 ≦ η ₁ + η ₂ ≦
Set to 2.0. α _i (1 ≦ i ≦ m) is a real number such that α _i > 0, and β _i (1 ≦ _i
i ≦ m) is a real number such that 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
˜1.5 and α _i = 0.1 to 0.8 (2 ≦ i ≦ m). Note that α _i + β _i-1 = 0.5 to _{i for} 3 ≦ i ≦ m
It is in the range of 1.5 and is constant regardless of i. )
In the order of α _i T (1 ≦ i ≦ m), recording light having a recording power Pw of Pw ≧ Pe for melting the recording layer is irradiated to β _i T (1 ≦ i ≦ m). ) Within the time of 0
<Pb ≦ 0.2Pe (however, in β _m T, 0 <
An optical information recording medium for performing recording by irradiating recording light with a bias power Pb such that Pb ≦ Pe. 23. The optical information recording medium according to claim 22 , wherein the light having a wavelength of 350 to 680 nm and the numerical aperture NA is 0.5.
When recording and reproducing data by converging on a recording layer through an objective lens of 5 to 0.9, 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 recording as ≦ Pe / Pw ≦ 0.6. 24. The optical information recording medium according to claim 22 , wherein the light having a wavelength of 600 to 680 nm and the numerical aperture NA is 0.5.
When recording and reproducing data with the shortest mark length in the range of 0.35 to 0.45 μm, the light is focused on the recording layer through the substrate through the objective lens of 5 to 0.65, and n is 1 to 14 , M = n−1, Pb is constant regardless of the linear velocity, and Pe / Pw can be changed in the range of 0.4 to 0.6 according to the linear velocity. (I) Recording In the linear velocity range of 3 to 4 m / s, the reference clock period T is To, α ₁ = 0.3 to 0.8, α ₁ ≧ α _i = 0.2 to 0.4, and Without 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, and α _i T (1 Within the time of ≦ i ≦ m), the recording power P
Irradiating the recording light of w ₁ , (ii) in the range of the recording linear velocity of 6 to 8 m / s, the reference clock period T is set to To / 2, α ′ ₁ = 0.3 to 0.8, α ′ ₁ ≧ α ′ _i = 0.3 to 0.5, which is constant regardless of i (2 ≦ i ≦ m), α ′ _i + β ′ _i−1 = 1.0 (3 ≦ i ≦ m), β ′ _m = 0 to 1.0, and the recording power P within the time of α _i T (1 ≦ i ≦ m)
When irradiating w ₂ recording light, α ′ _i > α _i (2 ≦ i ≦ m) and 0.8 ≦ Pw ₁ / P
An optical information recording medium for recording with w ₂ ≦ 1.2. 25. The optical information recording medium according to claim 22 , 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 is 6 to 10 m / s, and the recording area is composed of a plurality of zones separated by radii, and the recording density is almost equal to the average linear velocity in each zone. When recording is performed by changing the reference clock period T so as to be constant, m is kept constant regardless of the zone, and Pb / Pe and / or α _i (i is 1 ≦ An optical information recording medium for recording by monotonically decreasing at least one of i ≦ m). 26. The optical information recording medium according to claim 25 , wherein the recording area is divided into p zones by a radius.
The innermost side is the first zone, the outermost side is the p-th zone, 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 , Maximum linear velocity <
v _{q> max,} the 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 1 In the range of 2-3.
_{<V q> max / <v} q> min is less than or equal to 1.5, within (i) the same _{zone, ω q, T q, α} i, β i, Pe,
Pb and Pw are constant, the physical length n _{min Tq} < _vq > _ave of the shortest mark is 0.5 μm or less, and _Tq < _vq.
> _Ave is almost 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, and (ii) Pb, Pw, Pe / Pw, α _i for each zone
(1 ≦ i ≦ m), β ₁ and β _m are variable, and at least α _i (i is 2 ≦ i from the outer zone toward the inner zone).
An optical information recording medium for recording by monotonically decreasing at least one of ≦ m). 27. The maximum value of Pw in the recording area is P
When w _max and the minimum value are Pw _min , Pw _max / Pw _min
27. The optical information recording medium according to claim 26 , wherein ≦ 1.2. 28. An optical information recording medium according to any one of claims 25 to 27, the light of wavelength 600～680Nm, numerical aperture NA is 0.5
When recording and reproducing data by passing light through an objective lens of 5 to 0.65 to a recording layer via a substrate, the innermost circumference of the recording area is in a range 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 circumferential zone is 3 to 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. Let the linear velocity be <v _q > _ave , the maximum linear velocity be <v _q > _max , the minimum linear velocity be <v _q > _min , the reference clock period be T _q , and the time length of the shortest mark be n _min T _q. , N is an integer of 1 to 14, m = n−1, ω _q , Pb and Pe / Pw are constant regardless of zones, and T _q <v _q > _ave is 1 ≦ q ≦ p. It is substantially constant for all q, and Equation 4] _{(<v q> max - <} v q> min) / (<v q> max + v _q>
min ) <10%, and (i) in the first zone, α ¹ ₁ = 0.3 to 0.8, α ¹ ₁ ≧ α ¹ _i = 0.2 to 0.4, and Constant (2 ≦ i ≦ m), α ¹ ₂ + β ¹ ₁ ≧ 1.0, α ¹ _i + β ¹ _i-1 = 1.0 (3 ≦ i ≦ m), and (ii) in the p-th zone , Α ^p ₁ = 0.3 to 0.8, α ^p ₁ ≧ α ^p _i = 0.3 to 0.5, which is constant regardless 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
An optical information recording medium for recording by setting ^p _i (2 ≦ i ≦ m) and α ^q ₁ being a value between α ¹ ₁ and α ^p ₁ . 29. α ¹ ₁ ≧ α ^q ₁ ≧ α ^p ₁ (where α ¹ ₁ > α
^29. The optical information recording medium according to claim 28 , wherein the optical information recording medium is used for recording by setting ^p ₁ ). 30. A _{Pb, Pe / Pw, β 1} , β m is constant irrespective of the zone, alpha billing for recording by ₁ and alpha _i and (2 ≦ i ≦ m) can be changed by the zone Term
28. The optical information recording medium described in 28 or 29 . 31. At least Pe / Pw, Pb, Pw,
^{_{β m, (α 1 1,}} α p 1), the value of ^{_{(α 1 c, α p c}} ), on a pre-substrate, in any one of claims 28 to 30 is described by the pre-pit train or groove deformation The optical information recording medium described. 32. By pre-pit row or groove deformation,
An optical information recording medium having recorded in advance on the substrate the address information, together with the address information, to claim 28 including the information about the appropriate alpha ₁ and _{α i (2 ≦ i ≦ m} ) in said address 31 The optical information recording medium according to any one of 1. 33. The optical information recording medium according to claim 1 , wherein an erasing power P capable of crystallizing an amorphous material is provided between recording marks.
When the recording light of e is irradiated and the time length of one recording mark is nT (T
Is a reference clock period, n is an integer of 2 or more), and the time length nT of the recording mark is expressed by 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 = n−k, and k is 0 ≦ k
≤2. Further, Σ _i (α _i + β _i ) + η ₁ + η ₂ = n, and η ₁ is η ₁
Real number ≧ 0, η ₂ is a real number η ₂ ≧ 0, 0 ≦ η ₁ + η ₂ ≦
Set to 2.0. α _i (1 ≦ i ≦ m) is a real number such that α _i > 0, and β _i (1 ≦ _i
i ≦ m) is a real number such that β _i > 0. α ₁ = 0.1 to 1.5, β ₁ = 0.3 to 1.0, β _m = 0
Is set to 1.5, and α _i is 0.1 when _i is 2 ≦ i ≦ m.
It is in the range of 0.8, and is constant regardless of i. Note that α _i + β _i-1 is 0.5 to 0.5 for _{i where} 3 ≦ i ≦ m.
It is in the range of 1.5 and is constant regardless of i. )
In the order of α _i T (1 ≦ i ≦ m), recording light having a recording power Pw of Pw ≧ Pe for melting the recording layer is irradiated to β _i T (1 ≦ i ≦ m). ) Within the time of 0
<Pb ≦ 0.2Pe (however, in β _m T, 0 <
Recording light with bias power Pb of Pb ≦ Pe) is applied, and m, α _i + β _i−1 (3 ≦ i ≦ m), α
An optical information recording medium for recording by keeping ₁ T and α _i T (2 ≦ i ≦ m) constant and changing β _m monotonically as the linear velocity decreases. 34. The maximum recording power at each recording linear velocity is P
When w _max and the minimum recording power are Pw _min , Pw _max / Pw _min ≦ 1.2, Pe / Pw = 0.4 to 0.6, 0 ≦ Pb ≦ 1.5 (mW) 34. The optical information recording medium according to claim 33 , wherein 35. When the recording linear velocity is 5 m / s or less,
請 for performing recording by a Σα _i <0.5n
The optical information recording medium according to claim 34 . 36. β _m at the maximum recording linear velocity is set to β ^H _m ,
When the the β _m β ^L _m at the minimum recording linear velocity, the beta _m in other recording linear velocity, and a value between beta ^L _m and beta ^H _m, Pb irrespective of the recording linear velocity, the Pe / Pw 36. The optical information recording medium according to claim 34 or 35 , wherein recording is performed by keeping the value constant. 37. The optical information recording medium according to claim 33, wherein recording is performed by keeping β _m constant regardless of the recording linear velocity. 38. At least Pe / Pw ratio, Pb, P
_{w, α 1 T, α i} T (2 ≦ i ≦ m), (β L m, β H m) figures are on in advance a substrate, according to claim 36 which is recorded by the pre-pit train or groove deformation Optical information recording medium. 39. The optical information recording medium according to claim 1 , comprising a predetermined recording area, the recording area being divided into p zones having a uniform width in a radial direction, An optical information recording medium for recording information by a plurality of mark lengths by rotating at a constant angular velocity regardless of position, wherein a groove having a predetermined groove meandering signal is formed on a substrate, and the groove meandering is performed. The reference period of the signal changes for each zone, and the average linear velocity in the q-th zone (where q is an integer of 1≤q≤p) is <v _q > _ave , the maximum linear velocity is <v _q > _max , and the minimum. Assuming that the linear velocity is <v _q > _min and the reference period of the groove meandering signal is Tw _q , <v _q > _ave Tw _q is constant, and the following equation (6) (<v _q > _max − <v _q > _min ) / (< _Vq > _max + < _vq >
_min ) <1% of optical information recording medium. 40. One zone of the groove is defined as one zone, and the groove has a meandering with a constant period regardless of the zones. When the groove pitch is TP and the meandering period is Tw ₀ , approximately: The optical information recording medium according to claim 39 , wherein the relationship of 2π · TP = a · Tw ₀ · v ₀ (where a is a natural number) is satisfied. 41. The optical information recording medium according to claim 1 , which has a predetermined recording area, and the recording area is divided into p zones having a uniform width in the radial direction (however, , P is 20
An integer of 0 or more), an optical information recording medium for recording information by a plurality of mark lengths by rotating at a constant angular velocity irrespective of the radial position, the groove having a predetermined groove meandering signal on a substrate. Is formed, the reference period of the groove meandering signal changes for each zone, the average linear velocity in the q-th zone (where q is an integer of 1 ≦ q ≦ p) is <v _q > _ave , If the reference period is _{Tw q, <v q> ave} Tw q is an optical information recording medium is constant. 42. The innermost circumference of the recording area has a radius of 20-2.
The optical information recording medium according to claim 41 , wherein the optical information recording medium is in the range of 5 mm and the outermost circumference is in the range of 55 to 60 mm in radius. 43. When recording information on the optical information recording medium according to claim 1 , an erasing power P capable of crystallizing an amorphous material is provided between recording marks.
When the recording light of e is irradiated and the time length of one recording mark is nT (T
Is a reference clock period, n is an integer of 2 or more), and the time length nT of the recording mark is expressed by 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 = n−k, and k is 0 ≦ k
≤2. Further, Σ _i (α _i + β _i ) + η ₁ + η ₂ = n, and η ₁ is η ₁
Real number ≧ 0, η ₂ is a real number η ₂ ≧ 0, 0 ≦ η ₁ + η ₂ ≦
Set to 2.0. α _i (1 ≦ i ≦ m) is a real number such that α _i > 0, and β _i (1 ≦ _i
i ≦ m) is a real number such that 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
˜1.5 and α _i = 0.1 to 0.8 (2 ≦ i ≦ m). Note that α _i + β _i-1 = 0.5 to _{i for} 3 ≦ i ≦ m
It is in the range of 1.5 and is constant regardless of i. )
In the order of α _i T (1 ≦ i ≦ m), the recording light having a recording power Pw of Pw ≧ Pe for melting the recording layer is irradiated within a time of α _i T (1 ≦ i ≦ m), and β _i T (1 ≦ i ≦ m ) Within the time of 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 having a bias power Pb such that Pb ≦ Pe. 44. 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, wherein 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 = The optical recording method according to claim 43 , wherein 1.0 (3 ≤ i ≤ m), 0 ≤ Pb ≤ 1.5 (mW), and 0.3 ≤ Pe / Pw ≤ 0.6. The 45. wavelength of 600~680nm light, the numerical aperture NA is passed through the objective lens of 0.55 to 0.65, is focused on the recording layer through the substrate, the shortest mark length 0.35
An optical recording method for recording and reproducing data in a range of up to 0.45 μm, n is an integer from 1 to 14, m = n−1, Pb is constant regardless of linear velocity, and Pe / Pw Is variable in the range of 0.4 to 0.6, and (i) in the range of the recording linear velocity of 3 to 4 m / s, the reference clock period T is To, and α ₁ = 0. .3 to 0.8, α ₁ ≧ α _i = 0.2 to 0.4, which is constant regardless 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 α _i T (1 Within the time of ≦ i ≦ m), the recording power P
Irradiating the recording light of w ₁ , (ii) in the range of the recording linear velocity of 6 to 8 m / s, the reference clock period T is set to To / 2, α ′ ₁ = 0.3 to 0.8, α ′ ₁ ≧ α ′ _i = 0.3 to 0.5, which is constant regardless of i (2 ≦ i ≦ m), α ′ _i + β ′ _i−1 = 1.0 (3 ≦ i ≦ m), β ′ _m = 0 to 1.0, and the recording power P within the time of α _i T (1 ≦ i ≦ m)
When irradiating w ₂ recording light, α ′ _i > α _i (2 ≦ i ≦ m) and 0.8 ≦ Pw ₁ / P
The optical recording method according to claim 43 or 44 , wherein w ₂ ≦ 1.2. 46. 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 2. The medium is rotated so that the linear velocity at the outermost periphery of the recording area becomes 4 to 10 m / s, and the recording area consists of a plurality of zones separated by a radius, and the average linear velocity in each zone is According to the recording method, the reference clock period T is changed so that the recording density becomes substantially constant, in which m is kept constant regardless of the zone, and Pb / Pe and / or α from the outer zone toward the inner zone. The optical recording method according to claim 43 , wherein _i (i is at least one of 1 ≦ i ≦ m) is monotonically decreased. 47. The recording area is divided into p zones by radius, the innermost side being the first zone, the outermost side being the pth zone, and the qth zone (where q is 1 ≦ q ≦ p an angular velocity in an integer) omega _q, the average linear velocity <v
_q > _ave , maximum linear velocity <v _q > _max , minimum linear velocity <v _q
> _Min, the reference clock period T _q, 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,
_{<V q> max / <v} q> min is less than or equal to 1.5, within (i) the same _{zone, ω q, T q, α} i, β i, Pe,
Pb and Pw are constant, the physical length n _{min Tq} < _vq > _ave of the shortest mark is 0.5 μm or less, and _Tq < _vq.
> _Ave is almost 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, and (ii) Pb, Pw, Pe / Pw, α _i for each zone
(1 ≦ i ≦ m), β ₁ and β _m are variable, and at least α _i (i is 2 ≦ i from the outer zone toward the inner zone).
46. At least one of ≦ m) is monotonically decreased.
The optical recording method described in. 48. The maximum value of Pw in the recording area is P
When w _max and the minimum value are Pw _min , Pw _max / Pw _min
The optical recording method according to claim 47 , wherein ≦ 1.2. 49. Optical recording for recording / 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 through a substrate. In the method, the innermost circumference of the recording area has a radius of 20 to 25 mm, the outermost circumference has a radius of 55 to 60 mm, and the average linear velocity of the innermost circumference side zone is 3 to 4 m / s. Then, 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. _{When q} > _min , the reference clock period is T _q , and the temporal length of the shortest mark is n _min T _q , n is an integer of 1 to 14, m = n−1, and ω _q , Pb, and Pe. / Pw are constant irrespective of the zone, T _q <v _{q> ave} is substantially against 1 ≦ q ≦ p becomes all q It is a constant, and Equation 9] _{(<v q> max - <} v q> min) / (<v q> max + <v q>
_min ) <10%, and (i) in the first zone, α ¹ ₁ = 0.3 to 0.8, α ¹ ₁ ≧ α ¹ _i = 0.2 to 0.4, and Constant (2 ≦ i ≦ m), α ¹ ₂ + β ¹ ₁ ≧ 1.0, α ¹ _i + β ¹ _i-1 = 1.0 (3 ≦ i ≦ m), and (ii) in the p-th zone , Α ^p ₁ = 0.3 to 0.8, α ^p ₁ ≧ α ^p _i = 0.3 to 0.5, which is constant regardless of i (2 ≦ i ≦ m), α ^p _i + β ^p _{i −1} = 1.0 (2 ≦ i ≦ m), and (iii) in other zones, α ¹ _i ≦ α ^q _i ≦ α
^49. The optical recording method according to claim 46, wherein ^p _i (2 ≦ i ≦ m) and α ^q ₁ is a value between α ¹ ₁ and α ^p ₁ . 50. α ¹ ₁ ≧ α ^q ₁ ≧ α ^p ₁ (where α ¹ ₁ > α
The optical recording method according to claim 49 , wherein the optical recording method is ^p ₁ ). 51. _{Pb, Pe / Pw, β 1} , β m is constant irrespective of the _{zone, α 1, α i (2} ≦ i ≦ m) only the claim 49 or 50 is changed by the zone Optical recording method. 52. When recording information on the optical information recording medium according to claim 1 , an erasing power P capable of crystallizing an amorphous material is provided between recording marks.
When the recording light of e is irradiated and the time length of one recording mark is nT (T
Is a reference clock period, 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 = n−k, and k is 0 ≦ k
≤2. Further, Σ _i (α _i + β _i ) + η ₁ + η ₂ = n, and η ₁ is η ₁
Real number ≧ 0, η ₂ is a real number η ₂ ≧ 0, 0 ≦ η ₁ + η ₂ ≦
Set to 2.0. α _i (1 ≦ i ≦ m) is a real number such that α _i > 0, and β _i (1 ≦ _i
i ≦ m) is a real number such that β _i > 0. α ₁ = 0.1 to 1.5, β ₁ = 0.3 to 1.0, β _m = 0
Is set to 1.5, and α _i is 0.1 when _i is 2 ≦ i ≦ m.
It is in the range of 0.8, and is constant regardless of i. Note that α _i + β _i-1 is 0.5 to 0.5 for _{i where} 3 ≦ i ≦ m.
It is in the range of 1.5 and is constant regardless of i. )
In the order of α _i T (1 ≦ i ≦ m), the recording light having a recording power Pw of Pw ≧ Pe for melting the recording layer is irradiated within a time of α _i T (1 ≦ i ≦ m), and β _i T (1 ≦ i ≦ m ) Within the time of 0
<Pb ≦ 0.2Pe (however, in β _m T, 0 <
Recording light with bias power Pb of Pb ≦ Pe) is applied, and m, α _i + β _i−1 (3 ≦ i ≦ m), α
An optical recording method characterized in that ₁ T and α _i T (2 ≦ i ≦ m) are kept constant and β _m monotonically increases as the linear velocity decreases. 53. The maximum recording power at each recording linear velocity is set to P
When w _max, the minimum recording power and _{Pw min, Pw max / Pw min} ≦ 1.2, Pe / Pw = 0.4~0.6, claim 52 is 0 ≦ Pb ≦ 1.5 (mW) The optical recording method described in. 54. A recording linear velocity of 5 m / s or less,
The optical recording method according to claim 53 , wherein Σα _i <0.5n. 55. At the maximum recording linear velocity, β _m is β ^H _m ,
When the the β _m β ^L _m at the minimum recording linear velocity, the beta _m in other recording linear velocity, and a value between beta ^L _m and beta ^H _m, Pb irrespective of the recording linear velocity, Pe / Pw ratio The contract that is constant
The optical recording method according to claim 53 . 56. β _m is constant regardless of the recording linear velocity.
The optical recording method according to claim 52 . 57. A method for recording information with 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 the above, recording is performed at a constant linear velocity, and the ratio v _out / v _in of the recording linear velocity v _in in the innermost zone and the recording linear velocity v _out in the outermost zone is 1.2 to 2. Request to change β _m according to the linear velocity in each zone
Item 57. The optical recording method according to any one of items 52 to 56 . 58. A method of recording information with 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 the above, recording is performed at a constant linear velocity, and the ratio v _out / v _in of the recording linear velocity v _in in the innermost zone and the recording linear velocity v _out in the outermost 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 regardless of the linear velocity
The optical recording method according to claim 43 , wherein ₁ T, Pe / Pw, and Pb are kept constant, and α _i and / or β _m are changed according to the linear velocity. 59. When recording information on the optical information recording medium according to any one of claims 39 to 42 , the reference clock cycle T _q is the reference cycle Tw _q of the groove meander of each zone. An optical recording method characterized by generating as a multiple or a divisor.