JP2003303443A - Phase-change type recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase-change type recording medium wherein no noise such as jitters is generated even for the low output light of a short wavelength, O/W characteristics are good, archival characteristics are good, and high-density recording is carried out. <P>SOLUTION: A layer structure is made by disposing at least a first recording constituting layer 100, a resin middle layer 6 and a second recording constituting layer 200 in this order on a substrate 1, the first recording constituting layer comprises a reflective heat radiation layer 2, a first protective layer 3, a first recording layer 4 and a second protective layer 5 sequentially from the substrate side 1, the second recording constituting layer comprises a third protective layer 7, an Ag or Ag alloy layer 8, a fourth protective layer 9, a second recording layer 10 and a fifth protective layer 11 sequentially from the resin middle layer side, the first and second recording layers contain at least SbTe, the linear expansion coefficient of the third protective layer is 3.0×10<SP>-6</SP>to 10×10<SP>-6</SP>, and a light transmittance is 80% or higher. <P>COPYRIGHT: (C)2004,JPO

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 (phase change recording medium) for high density recording having a phase change recording layer such as R.

[0002]

2. Description of the Related Art Generally, a compact disc (CD) or a D
The VD is performed by detecting a binary signal recording and a tracking signal 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, a phase change type rewritable compact disc (CD
In addition to the widespread use of -RW: CD-Rewritable, various phase change type rewritable DVDs have been proposed as DVDs. In addition, while the DVD capacity is 4.7 GB, the recording / reproducing wavelength is 390 n
Numerical aperture NA (Numer)
A system DVR has been proposed in which the capacity of the IC is increased to 20 GB or more (for example,
ISOMTechnical Digest, '00
(2000), 210).

These phase change type rewritable CDs and DVs
The D and DVR detect the recorded information signal by utilizing the reflectance difference and the phase difference change caused by the refractive index difference 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 reflectance difference and the phase difference are utilized by utilizing the multiple interference of these constituent layers. Can be controlled to have compatibility 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 where the reflectance is reduced to about 15 to 25%, and in the CD drive added with the amplification system that covers the low reflectance. It can be regenerated. Since the phase-change recording medium can perform the erasing and re-recording processes only by the intensity modulation of one focused light beam, in a phase-change recording medium such as a CD-RW and a rewritable DVD, recording is recording. Overwrite (O / W) recording that simultaneously erases and erases is included.

To record information using phase change, a crystal,
An amorphous state or a mixed state thereof can be used, and a plurality of crystalline phases can be used, but the rewritable phase-change recording medium currently in practical use has an unrecorded / erased state as a crystalline state. Generally, an amorphous mark is formed and recorded.

As the material of the phase change recording layer, chalcogenide alloys containing chalcogen elements, that is, S, Se and Te are often used. For example, GeTe-Sb
GeSbTe system whose main component is ₂ Te ₃ pseudo binary alloy,
I based on the InTe-Sb ₂ Te ₃ pseudo-binary alloy
Examples thereof include nSbTe system, AgInSbTe system and GeSbTe system containing Sb _0.7 Te _0.3 eutectic alloy as a main component. Among, GeTe-Sb ₂ Te ₃ pseudo-binary alloy added with system excess Sb in, in particular Ge ₁ Sb ₂ Te _4, or G
Compositions in the vicinity of intermetallic compounds such as e ₂ Sb ₂ Te ₅ have been mainly put into practical use. These compositions are characterized by crystallization without the phase separation peculiar to intermetallic compounds, and because the crystal growth rate is fast, initialization is easy, and the recrystallization rate during erasing is fast. Therefore, a pseudo binary alloy system or a composition in the vicinity of an intermetallic compound has been attracting attention as a recording layer exhibiting a practical overwrite (O / W) characteristic (Reference Jpn. J. App.
l. Phys. , Vol. 69 (1991), p284
9, or SPIE, vol. 2514 (199
5), pp294-301, etc.).

Further, it has been reported that the GeSbTe ternary composition or the composition of the recording layer containing the additive element with the ternary composition as a matrix is disclosed in the prior art (JP-A-61-2).
58787, 62-53886, and 62.
-152786, JP-A-1-63195,
1-211249 and 1-277338). However, in order to apply a material having such a composition to a rewritable DVR or other optical recording medium for high-density recording, development has just begun and there are many problems to be solved. In particular, in the case of an optical system having a short wavelength such as a blue laser, the beam output is low, so that there is a drawback that noise easily occurs in the recording layer, it is difficult to satisfy the overwrite (O / W) characteristics, and high speed and high density are achieved. It has become an issue in recording.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to suppress noise such as jitter even for low output light having a short wavelength such as a blue laser. An object of the present invention is to provide a phase change recording medium which has excellent / W characteristics and archival characteristics and which enables high density recording.

[0008]

In order to solve the above-mentioned problems, a phase-change recording medium according to the present invention has at least a first recording constituent layer, a resin intermediate layer, and a second recording constituent layer on a substrate. The first recording component layer has a reflective heat radiation layer, a first protective layer, a first recording layer, and a second recording layer in this order from the substrate side.
The second recording constituent layer is composed of a third protective layer, an Ag or Ag alloy layer, a fourth protective layer, a second recording layer and a fifth protective layer in this order from the resin intermediate layer side. The first recording layer and the second recording layer contain at least SbTe, and the linear expansion coefficient of the third protective layer is 3.0 × 10 ⁻⁶ to 1.
By setting the light transmittance to 0 × 10 ^-6 and the light transmittance to 80% or more, noise such as jitter is suppressed, and O / W characteristics, archival characteristics, and high density recording performance are improved. .

That is, a recording medium according to a first aspect is a phase change type recording medium utilizing a phase transition phenomenon of crystal and amorphous by light irradiation, and the constituent layers are sequentially formed.
For example, a reflection and heat dissipation layer made of an Ag alloy is provided on a substrate having guide grooves formed therein, the first protective layer and the second protective layer are made of, for example, a mixed composition of ZnS and SiO ₂ , and SbTe is a main constituent element. And a so-called reflection heat dissipation layer to a second protective layer, which are laminated layers of the first recording layer contained as the first recording layer for recording on the first recording layer. Then, the linear expansion coefficient is further 3.0 × 10 ⁻⁶ to 10 × 10 ⁻⁶ , and the linear expansion coefficient is ^{higher than} that of the light through the intermediate layer in which the groove is formed by the transparent resin such as the UV resin on the second protective layer. 8 transmittance
A third protective layer of 0% or more and an Ag or Ag alloy layer adjacent thereto are provided, the fourth protective layer and the fifth protective layer are made of, for example, a mixed composition of ZnS and SiO ₂ , and SbTe is a main constituent element. A second recording layer for recording on the second recording layer, a so-called third protective layer to a fifth protective layer having a laminated second recording layer.

As described above, the recording layers are composed of two layers, and each recording layer contains at least SbTe so that small marks can be easily formed to support high density recording.
The linear expansion coefficient is 3.0 × 10 ^-6 to 1 in the middle of the two recording layers.
A third protective layer having a light transmittance of 80% or more and 0 × 10 ⁻⁶ or less, and an Ag or Ag alloy layer having a thickness of 20 nm or less are formed adjacent to the third protective layer to improve heat dissipation. Absorbs deformation caused by heat. That is, the recording wavelength 405
Ag or A with high light transmittance and thermal conductivity near nm
The heat dissipation is further improved by using g alloy
The / W characteristic is improved and high density recording is possible.

In the phase-change recording medium of the present invention, the component for forming the third protective layer is Be ₂ O ₃ (claim 2) or a mixed system composition of Al ₂ O ₃ and SiO ₂ (claim 3). ), Or a mixed system composition of MgO and SiO ₂ (claim 4), a mixed system composition of In ₂ O ₃ and ZnO (claim 5), or a mixed system composition of In ₂ O ₃ and SnO ₂ (claim 5). According to claim 6) or a mixed system composition of In ₂ O ₃ , ZnO and SnO ₂ (claim 7), it is possible to cope with the thermal volume change at the time of O / W.
The / W characteristic is improved, high density recording is realized, and the archival characteristic is also improved.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a schematic cross-sectional view of a layer structure showing an example of the phase-change recording medium of the present invention, which includes substrate 1 / reflection heat dissipation layer 2 / first protective layer 3 / first recording layer 4 / Second
Protective layer 5 / resin intermediate layer 6 / third protective layer 7 / Ag or A
The g alloy layer 8 / the fourth protective layer 9, the second recording layer 10, the fifth protective layer 11, the adhesive layer 12, and the cover substrate 13 are included. The order of the layers as shown in FIG. 1 is suitable for irradiating each recording layer with a focused light beam for recording and reproduction, for example, a laser beam through the transparent cover substrate 13.

Substrate 1 in the phase change recording medium of the present invention
As the material of, a transparent resin such as polycarbonate, acrylic resin, or polyolefin, or transparent glass can be used. Among them, polycarbonate resin has a track record of being most widely used in CD,
It is also the most preferable material because it is inexpensive. Board 1
Usually, a groove having a pitch of 0.8 μm or less for guiding the recording / reproducing light is provided, but this groove does not necessarily have to be a geometrically rectangular or trapezoidal groove. The grooves may be formed optically by forming different kinds of waveguides.

Next, the material of the first recording layer 4 and the second recording layer 10 in the phase-change recording medium of the present invention is a thin film whose main component is an alloy containing Sb and Te as main constituent elements. As such an alloy, there is, for example, one containing Ge, Sb, or Te as a constituent element. If necessary, other elements may be added to the respective recording layers made of such constituent elements up to a total of about 10 atomic%. Further, each recording layer further contains at least one element selected from O, N or S in an amount of 0.1 atom% or more, 5
The optical constant of the recording layer can be finely adjusted by adding at most atomic%. However, the addition of more than 5 atom% is not preferable because it lowers the crystallization rate and deteriorates the erasing performance.

Further, in order to increase the temporal stability without decreasing the crystallization rate during overwriting (O / W), V, N
It is preferable to add at least one element selected from b, Ta, Cr, Co, Pt, and Zr in an amount of 8 atomic% or less.
More preferably, it is 0.1 atom% or more and 5 atom% or less. It is desirable that the total addition amount of the additional element and Ge with respect to SbTe is 15 atomic% or less. 15 atom%
If it is contained in excess, 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.

In order to improve stability over time and finely adjust the refractive index, it is preferable to add at least one of Si, Sn and Pb in an amount of 5 atomic% or less. The total addition amount of these additional elements and Ge is preferably 15 atomic% or less. In addition, S
Each element of i, Sn, or Pb is an element having a four-coordination network like Ge.

Further, by adding Al, Ga and In in an amount of 8 atomic% or less, the crystallization temperature can be increased and at the same time jitter can be reduced and recording sensitivity can be improved, but segregation is likely to occur. It is preferably 6 atomic% or less. The total addition amount of Al, Ga, and In is 15 atomic% or less, preferably 13% as a total addition amount including Ge.
The following is desirable. Adding Ag in an amount of 8 atomic% or less is effective in improving recording sensitivity,
In particular, when the Ge atomic weight exceeds 5 atomic%, the effect is remarkable. However, if the added amount of Ag exceeds 8 atomic%, jitter is increased and the stability of the amorphous mark is impaired, which is not preferable. Further, if the total addition amount including Ge exceeds 15 atom%, segregation easily occurs, which is not preferable. The most preferable content of Ag is 5 atom%.
It is the following.

The first recording layer 4 of the phase change recording medium of the present invention
The second recording layer 10 and the second recording layer 10 are phase change recording layers, and the thickness thereof is generally preferably in the range of 5 nm to 100 nm. The thickness of the first recording layer 4 and the second recording layer 10 is 5 nm.
If it is thinner, it is difficult to obtain a 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. The contrast needs to be compatible with a read-only disc such as a DVD.

In high-density recording in which the shortest mark length is 0.5 μm or less, the recording layer has a thickness of 5 nm or more and 2
It is preferably 5 nm or less. If it 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 tend to appear, which is not preferable. On the other hand, if it is thicker than 25 nm, the heat capacity becomes large and the recording sensitivity becomes poor. Also, the crystal growth becomes three-dimensional, so that the edges of the amorphous marks are disturbed and the jitter tends to increase. Furthermore, the volume change due to the phase change of the first recording layer 4 and the second recording layer 10 becomes remarkable, and the repeated overwrite (O / W) durability deteriorates, which is not preferable. From the viewpoints of mark edge jitter and repeated overwrite (O / W) durability, it is more desirable to set it to 20 nm or less.

It is desirable that the density of each of the first recording layer 4 and the second recording layer 10 is 80% or more, more preferably 90% or more of the bulk density. The densities of the first recording layer 4 and the second recording layer 10 are set so that the pressure of the sputter gas (rare gas such as Ar) at the time of film formation is lowered in the sputter film formation method, or the substrate is placed close to the front surface of the target. It is necessary to increase the amount of high-energy Ar irradiated on the recording layer by disposing it or the like. The high-energy Ar is the Ar ions irradiated on the target for sputtering, which are partially repelled and reach the substrate side, or Ar ions in plasma.
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 referred to as an "atomic peening effect". In the case of sputtering with Ar gas that is generally used, Ar is owing to the atomic peening effect.
Are mixed in the sputtered film. Ar in the mixed film
The amount can be used to estimate the atomic peening effect. 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, when the amount of Ar is large, the irradiation of high energy Ar is intense and the density is high, but the Ar taken into the film is deposited as voids during repeated overwrite (O / W), deteriorating the durability of repetition. Let A suitable amount of Ar in the recording layer film is 0.1 atomic% or more,
It is 1.5 atomic% 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 addition, the first recording layer 4 and the second recording layer 10 of the phase-change recording medium of the present invention are usually in a state after film formation.
It is amorphous. Therefore, it is necessary to crystallize the entire surface of each recording layer after the film formation so that the recording layer is initialized (unrecorded state). As an initialization method, initialization by solid phase annealing is possible, but initialization by so-called melt recrystallization in which the recording layer is once melted and gradually cooled during resolidification to be crystallized is desirable. Each of the above recording layers has almost no crystal growth nuclei immediately after film formation, and it is difficult to crystallize in a solid phase.However, according to melt recrystallization, a small number of crystal nuclei are formed and then melted. Recrystallization progresses at a high speed mainly by crystal growth. Since the crystals of the first recording layer 4 and the second recording layer 10 due to the melt recrystallization and the crystals due to the annealing in the solid phase have different reflectances, if mixed, they will cause noise. And
During actual overwrite (O / W) recording, the erased portion becomes crystals due to melt recrystallization, and therefore it is preferable that the initialization is also performed by melt recrystallization.

At the time of initialization by melt recrystallization, it is preferable to melt the recording layer locally and in a short time of about 1 millisecond or less. The reason for this is that 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. To give a thermal history suitable for initialization, a wavelength of 6
It is preferable that a high-power semiconductor laser beam of about 100 nm to 1000 nm is focused on the long axis of 100 to 300 μm and the short axis of 1 to 3 μm to be irradiated, and scanning is performed at a linear velocity of 1 to 10 m / s with the short axis direction as the scanning axis. . Even with the same focused light, if it is close to a circle, the melting region becomes too wide, 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 the melt recrystallization. That is, the recording medium having the recording power Pw for melting the recording layer focused to a spot diameter smaller than about 1.5 μm is applied to the medium after the initialization at a constant DC 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 erase power Pe (≦ P
If the reflectance in the erased state obtained by irradiating the erasing light of w) with a direct current is almost the same as the reflectance in the unrecorded initial state, the initialized state can be confirmed as a melt recrystallized state.
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. In addition,
The fact that the reflectance in the initialized state Rini and the reflectance in the molten recrystallized state Rcry are almost the same is (Rini-Rcry) /
It means that the difference between the reflectances defined by {(Rini + Rcry) / 2} is 20% or less. Usually, the reflectance difference is larger than 20% only by solid phase crystallization such as annealing.

As shown in FIG. 1, the first recording layer 4 and the second recording layer 10 of the present invention respectively include the first protective layer 3 and the second protective layer 5. The second recording layer 10 is sandwiched between the fourth protective layer 9 and the fifth protective layer 11, and the surface of the substrate 1 (groove forming surface) is formed.
It is provided above.

The protective layers of the first protective layer 3, the second protective layer 5, the fourth protective layer 9, and the fifth protective layer 11 of the present invention will be described below. The first protective layer 3 of the first recording constituent layer 100 prevents mutual diffusion of the first recording layer 4 and the reflection / heat dissipation layer 2 and suppresses deformation of the first recording layer 4 while efficiently moving to the reflection / heat dissipation layer 2. It also has the function of escaping heat. In addition, the second protective layer 5 is
It is effective mainly for preventing the deformation of the surface of the resin intermediate layer 6 due to the high temperature during recording. The fourth protective layer 9 of the second recording constituent layer 200 has a function of releasing heat to the second recording layer 10, the Ag or Ag alloy layer 8 and the third protective layer 7, and the second recording layer 1
0 also has a function of preventing mutual diffusion of Ag or the Ag or Ag alloy layer 8. The fifth protective layer 11 is effective for adjusting the reflectance and preventing the deformation of the adhesive layer 12 and the cover substrate 13 due to the high temperature during recording.

The materials for the first protective layer 3, the second protective layer 5, the fourth protective layer 9, and the fifth protective layer 11 include refractive index, thermal conductivity, chemical stability, mechanical strength and adhesion. It is decided in consideration of. As a material for forming each of the above-mentioned protective layers, it is desirable that the material has low thermal conductivity, but the standard is 1 × 10.
^-3 pJ / (μm · K · nsec). Note that it is difficult to directly measure the thermal conductivity of such a low thermal conductivity material in a thin film state, and a guideline can be obtained from thermal simulation and actual measurement results of recording sensitivity as an alternative to direct measurement. .

As a material for each of the above-mentioned protective layers having a low thermal conductivity which gives preferable results, at least one kind of ZnS, ZnO, TaS ₂ or rare earth sulfide is used in an amount of 50 mol.
%, 90 mol% or less, a high transparency, and a composite dielectric containing a heat-resistant compound having a melting point or a decomposition point of 1000 ° C. or more is desirable. More specifically, La, Ce,
Rare earth sulfides such as Nd and Y of 60 mol% or more, 90
A composite dielectric containing less than or equal to mol% is desirable. Or Z
nS, ZnO or rare earth sulfide composition range 70
It is desirable to set it to ˜90 mol%. Examples of the heat-resistant compound material having a melting point or decomposition point of 1000 ° C. or more to be mixed with these include Mg, Ca, Sr, Y, La and C.
e, Ho, Er, Yb, Ti, Zr, Hf, V, Nb,
Oxides such as Ta, Zn, Al, Si, Ge, and Pb, nitrides, carbides, and fluorides such as Ca, Mg, and Li can be used. Note that the above oxides, sulfides, nitrides, carbides, and fluorides do not necessarily have to have a stoichiometric composition, and it is also effective to control the composition for controlling the refractive index and the like, or to use them in mixture. Is.

As the respective protective layers of the first protective layer 3, the second protective layer 5, the fourth protective layer 9 and the fifth protective layer 11 of the present invention, the above-mentioned points of attention and the first recording layer 4 and the first recording layer 4 of the present invention are used. 2 recording layer 1
Considering the compatibility with the material forming 0, ZnS and S
A mixed composition with iO ₂ is most preferable. In the present invention, ZnS and SiO ₂ are mixed in each protective layer as described above, but using the same material in this way is also advantageous in terms of manufacturing cost reduction.

The function of each protective layer will be described in more detail. The layer structure of the present invention belongs to a type of layer structure called a quench structure. The rapid cooling structure employs a layer structure that promotes heat dissipation and increases the cooling rate during resolidification of the recording layer, thereby avoiding the problem of recrystallization during the formation of amorphous marks and improving the high-speed crystallization. Achieve an erase ratio.

The first protective layer 3 and the fourth protective layer 9 of the present invention
The film thickness of has a great influence on the durability against repeated overwrite (O / W), and is particularly important for suppressing the deterioration of jitter. The film thickness is generally 5 nm or more and 30 nm or less. When the thickness is less than 5 nm, the effect of delaying the heat conduction in the protective layer portion is insufficient and the recording sensitivity is significantly lowered, which is not preferable. If the film thickness is thicker than 30 nm, a sufficient flattening effect of the temperature distribution in the mark width direction cannot be obtained, and at the time of recording, the recording side and the heat radiating layer side of the second protective layer 5 and the fifth protective layer 11 respectively have a temperature. The difference becomes large, and the protective layer itself is likely 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. The detailed thicknesses of the first protective layer 3 and the fourth protective layer 9 are preferably 15 nm to 25 nm when the recording laser light wavelength is 600 to 700 nm, and 5 to 20 nm when the wavelength is 350 to 600 nm.
Is preferable, and more preferably 5 to 15 nm.

The thickness of the second protective layer 5 and the fifth protective layer 11 must be 5 nm or more and 30 nm or less. When 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.

When the phase change type recording layer material as described above is used, low jitter can be realized in high density recording with the shortest mark length of 0.3 μm or less, but according to the study by the present inventors, high density recording is realized. When a short wavelength laser diode (for example, a wavelength of 420 nm or less) is used for this purpose, further attention needs to be paid to the layer structure of the quenching structure. Particularly, the wavelength is 500 nm or less and the numerical aperture NA is 0.5.
In the study of the one-beam overwrite characteristic using a focused light beam of 5 or more, it was found that flattening the temperature distribution in the mark width direction is important for achieving a high erase ratio and a wide erase power margin. . The above tendency is the same in the DVR compatible optical system using the optical system having a wavelength of 390 to 420 nm and an NA of about 0.85.

The present inventors have made two
Considering the proper layer structure of the phase-change recording medium having the layer recording structure, it has light transmitting property, heat releasing property, and O / W.
The third protective layer 7 was configured so as to withstand thermal deformation due to, and a design was made to improve recording / reproducing characteristics, particularly O / W characteristics.

In the high density mark length modulation recording using the optical system as described above, one having a particularly low heat conduction characteristic is used as the second protective layer 5, and its thickness is preferably 7 n.
It is important that the thickness is not less than m and not more than 25 nm. For this reason, the third protective layer 7 provided on the second protective layer 5 needs to have a high thermal conductivity, and due to this configuration, heat does not suddenly escape during high-speed recording and a thermal gradient is formed. Therefore, high-speed recording becomes possible. The third protective layer 7 has a function of releasing heat and preventing deformation of the surface of the resin intermediate layer 6.

In the above, when only thermal conductivity is considered, the heat dissipation effect is promoted even if the thermal conductivity coefficient of the first protective layer 3 or the fourth protective layer 9 is increased, but the heat dissipation is promoted too much. Then, the irradiation power required for recording becomes high, which causes a problem that recording sensitivity is significantly lowered. Therefore, it is necessary to have a low thermal conductivity. By using a thin film protective layer having a low thermal conductivity, the number nse
Since the heat transfer from the recording layer to the heat dissipation layer can be delayed in time from c to several tens of nanoseconds and heat dissipation to the heat dissipation layer can be promoted thereafter, the recording sensitivity becomes higher than necessary due to the heat transfer characteristics of the protective layer. It does not lower. For these reasons, conventionally known SiO ₂ , Ta ₂ O ₅ , A
It is not preferable to use the protective layer material containing l ₂ O ₃ , AlN, SiN or the like as a main component alone because the thermal conductivity of the protective layer material itself is too high.

In the present invention, a protective layer having a linear expansion coefficient of 3.0 × 10 ^-6 to 10 × 10 ^-6 is formed as the third protective layer 7 to further improve the heat radiation effect as described later. For protection of the Ag or Ag alloy layer (2
(0 nm or less), the O / W characteristics of the second recording layer 10 were improved. In this case, if the light transmittance of the third protective layer 7 is 80% or more, even if the transmittance of the second recording constituent layer 200 is 40%, the first recording constituent layer 10
Since the reflectance from 0 can take a value equal to or higher than the reflectance of the substrate, recording and reproduction can be performed on any of the first recording layer 4 and the second recording layer 10.

As an example, a phase change having the constitution of the present invention, in which a third protective layer 7 (mixed composition of In ₂ O ₃ and SnO ₂ (ITO)) having a different linear expansion coefficient and an Ag layer having a thickness of 10 nm are provided, is provided. 2 shows the O / W characteristics of the second recording layer 10 of the type recording medium.
It was shown to. The linear expansion coefficient of the third protective layer 7 is 3.0 × 10 ^-6
At 10 × 10 ^-6 , the second recording layer 10 exhibits good O / W characteristics. From this, the linear expansion coefficient of the third protective layer 7 is controlled, and the thickness of the Ag or Ag alloy layer 8 is 20 n.
If it is m or less, the transmittance of Ag or Ag alloy layer is 8
Since it is 0% or more, the transmittance of the second recording constituent layer 200 is 4
It becomes 0% or more, and recording / reproducing of the first recording component layer 100 is sufficiently possible.

When Be ₂ O ₃ is used as the third protective layer 7 and the protective layer is formed under the conditions satisfying at least the above-mentioned characteristics, Be ₂ O ₃ has a high thermal conductivity, and therefore the second recording layer 10 is used for recording. The heat generated at this time is radiated in the third protective layer 7 via the Ag and Ag alloy layers. As a result, the recording layer containing the phase change material SbTe as a main component, which needs to be cooled rapidly, is in an optimally cooled state, and small amorphous marks can be formed.

Further, Al ₂ O ₃ and S are used as the third protective layer 7.
Mixed system composition with iO ₂ , mixed system composition with MgO and SiO ₂ , mixed system composition with In ₂ O ₃ and ZnO, In ₂ O ₃ and Sn
O ₂ mixed system (ITO) composition or In ₂ O ₃ and Zn
When the protective layer is formed using a mixed system composition of O and SnO ₂ , storage stability (archival property) is improved. In particular,
If chlorine or the like is contained in the material of the resin intermediate layer in a very small amount, not only the Ag or Ag alloy layer but also the recording layer will be corroded, so it is necessary to select a material having good storage stability. In the present invention, as a result of selecting the third protective layer 7 by paying attention to archival storability, the above-mentioned material showed good characteristics.

However, as the heat dissipation of the second recording constituent layer 200, the heat dissipation of the third protective layer 7 is not sufficient as described above, and the Ag and Ag alloy layers 8 improve the heat dissipation. In particular, in the recording layer based on SbTe, the first quenching property of heat forms an amorphous mark. Therefore, by combining Ag and the Ag alloy layer 8 and the third protective layer 7, a high density can be obtained. And O / W characteristics and storability are improved. Below, the reflection heat dissipation layer 2 and the Ag or Ag alloy layer 8 which perform a heat dissipation function are each demonstrated.

The reflection heat dissipation layer 2 is made of a material having a high thermal conductivity, so that the erase ratio and the erase power margin can be improved. As a result of examination, in order to exhibit the good erasing characteristics of the recording layer of the present invention in a wide erasing power range, not only the temperature distribution in the film thickness direction and the time change but also the film surface direction (with respect to the recording beam scanning direction) It is preferable to use a layer structure that can make the temperature distribution in the vertical direction as flat as possible. In the present invention, it has a very high thermal conductivity of 30
The feature is that the thin reflective heat dissipation layer 2 of 0 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 a difference in thermal conductivity even with the same composition.

The heat dissipation in the reflection heat dissipation layer 2 of the first recording component layer 100 can be achieved by increasing the thickness of the reflection heat dissipation layer 2, but when the thickness of the reflection heat dissipation layer 2 exceeds 300 nm, the first recording layer 4 is formed. The heat conduction in the film thickness direction becomes more remarkable than that in the film surface direction, and the effect of improving the temperature distribution in the film surface direction cannot be obtained. Also,
The heat capacity of the reflective heat dissipation layer 2 itself increases, and the reflective heat dissipation layer 2
Not only that, but it takes time to cool the first recording layer 4, which hinders the formation of amorphous marks. Most preferably, the reflective heat dissipation layer 2 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 release the heat from the first recording layer 4 to the reflective heat dissipation layer 2. Not enough attention was paid to the flattening of the temperature distribution in the direction.

Examples of the material of the reflection / heat dissipation layer 2 suitable for the present invention include Ag or Ag alloy, Cu alloy, Al alloy and the like. Examples of the Ag alloy include Ag or Ag alloys similar to those used in the Ag alloy layer 8 described later. When an Ag alloy is used as the reflection / heat dissipation layer 2, the preferable film thickness is 3
It is 0 nm or more and 200 nm or less. If it is less than 30 nm, the heat radiation effect is insufficient even with pure Ag. When it exceeds 200 nm, heat escapes in the vertical direction from the horizontal direction and does not contribute to the improvement of the heat distribution in the horizontal direction, and an unnecessary thick film reduces the productivity. In addition, the microscopic flatness of the film surface also deteriorates.

As the Cu alloy, for example, there is an Al--Cu alloy containing 0.3% by weight or more and 5.0% by weight or less of Cu. In particular, a mixed system composition of ZnS and SiO ₂ and Ta ₂
In the case of forming a two-layer constitution protective layer in which O ₅ is combined,
A containing 0.5% by weight or more and 4.0% by weight or less of Cu
The 1-Cu alloy is desirable as a reflection / heat dissipation layer that satisfies all of corrosion resistance, adhesion, and high thermal conductivity in a well-balanced manner. In addition, Si is 0.3 wt% or more, 0.8 wt% or less, Mg
Al-containing 0.3% by weight or more and 1.2% by weight or less
Mg-Si alloys are also effective.

As the Al alloy, for example, Al and Ta, T
i, Co, Cr, Si, Sc, Hf, Pd, Pt, M
There are alloys containing 0.2 atomic% or more and 2 atomic% or less of g, Zr, Mo or Mn, and these increase the volume resistivity in proportion to the concentration of the additive element and improve the hillock resistance. It can be used in consideration of durability, volume resistivity, film formation 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, although it depends 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.

When the above Al alloy is used as the reflection / heat dissipation layer 2, 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. As described above, when the thickness exceeds 300 nm, the heat escapes in the vertical direction from the horizontal direction and does not contribute to the improvement of the heat distribution in the horizontal direction, and the heat capacity of the reflection / radiation layer itself is large, so that the cooling rate of the recording layer becomes slow. In addition, the microscopic flatness of the film surface also deteriorates.

Next, the Ag or Ag alloy layer 8 will be described. In the second recording layer 10 of the present invention, the crystal growth at the time of resolidification near Tm is the rate-determining factor for recrystallization. The ultra-quenching structure is effective for maximizing the cooling rate in the vicinity of Tm to ensure the formation of the amorphous marks and the edges thereof, and flattening the temperature distribution in the film surface direction. Then, what was originally capable of high-speed erasing in the vicinity of Tm can reliably ensure erasing by recrystallization up to a higher erasing power. Therefore, when the so-called "super-quenching structure in which the heat conduction delay effect in the third protective layer 7 is taken into consideration" is applied to the second recording constituent layer 200 according to the present invention, the conventional GeTe-Sb ₂
It is more effective than the Te ₃ recording layer.

The Ag or Ag alloy layer 8 is used as the heat dissipation component layer for such ultra-quenching. Ag or A
When forming the g-alloy layer 8, the g-alloy layer 8 is formed later than the deposition-reflecting / reflecting heat-dissipating layer 2 at the time of film formation to eliminate the unevenness of the film thickness. The thickness of the Ag or Ag alloy layer 8 is preferably 5 nm or more and 20 nm or less. If it is 5 nm or less, it becomes non-uniform even if the deposition rate is slowed. As an Ag alloy, Ag, Cu, Ti, V, Ta, Nb, W, Co, Cr, Si,
Ge, Sn, Sc, Hf, Pd, Rh, Au, Pt, M
An alloy containing 0.2 atomic% or more and 5 atomic% or less of g, Zr, Mo or Mn is also desirable. When more importance is attached to stability over time, Ti and Mg are preferable as additive components.

The inventors of the present invention have described the reflective heat dissipation layer 2 and Ag.
Alternatively, it has been confirmed that the additive element to Al or the additive element to Ag in the Ag alloy layer 8 increases in volume resistivity in proportion to the concentration of the additive element. On the other hand, the addition of impurities is generally considered to reduce the crystal grain size, increase electron scattering at grain boundaries, and reduce the 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 reflection / heat dissipation layer 2 and Ag or Ag.
The alloy layer 8 is usually formed by a sputtering method or a vacuum evaporation method, but the total amount of impurities including the amount of water and oxygen mixed during film formation as well as the amount of impurities in the target and the evaporation material itself is 2 atomic% or less. And need to. For this reason, it is desirable that the ultimate vacuum of the process chamber is 1 × 10 ⁻³ Pa or less. Further, in the case of forming a film 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 atom%, the film formation rate is set to 1
It is desirable to prevent the addition of additional impurities as much as possible at 0 nm / sec or more.

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 crystalline phase and the amorphous phase depends on the film forming conditions. Further, 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 is determined by the method of manufacturing the alloy target used for sputtering and the sputtering gas (Ar, Ne, Xe, etc.).
Also depends on. As described above, the volume resistivity in the thin film state is not determined only by the metal material and the composition. In order to obtain high thermal conductivity, it is desirable to reduce the amount of impurities as described above, but on the other hand, pure metals such as Al and Ag tend to be inferior in corrosion resistance and hillock resistance. Therefore, it is necessary to determine the optimum composition.

It is also effective to make the reflection and heat dissipation layer 2 and the Ag or Ag alloy layer 8 multi-layered in order to obtain higher heat conduction and higher reliability. In this case, at least one layer is made of the high thermal conductivity material (low volume resistivity material) having a film thickness of 50% or more of the total layer thickness, which substantially contributes to the heat dissipation effect, and the other layers have corrosion resistance and It is configured so as to contribute to the improvement of adhesion to the protective layer and hillock resistance. More specifically, A, which has the highest thermal conductivity and the lowest volume resistivity among metals,
When g is used, if S (sulfide, etc.) is contained in the protective layer adjacent to Ag, the compatibility is poor and corrosion due to sulfidation is likely to occur, resulting in slight deterioration when repeatedly overwritten (O / W). Tends to be fast. In addition, corrosion tends to occur in an accelerated test environment of high temperature and high humidity. Therefore, when Ag or Ag alloy is used as the low volume resistivity material, it is also effective to provide an alloy layer containing Al as a main component between 1 nm and 100 nm inclusive as an interface layer between the adjacent protective layers. 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, similar to the above, for example, Ta, Ti, Co, Cr, Si, Sc, Hf, Pd,
An Al alloy containing Pt, Mg, Zr, Mo or Mn in an amount of 0.2 atomic% or more and 2 atomic% or less can be given. If the thickness of the interface layer is less than 1 nm, the protective effect is insufficient and the thickness is 100 nm.
If it exceeds, the heat dissipation effect will be sacrificed.

Further, 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. Incidentally, if the interface oxide layer exceeds 5 nm, especially 10 nm, it becomes a thermal resistance and the function as a reflection heat dissipation layer having an extremely high heat dissipation property which is the original purpose is impaired, which is not preferable.

In the present invention, in order to define the reflection heat dissipation layer 2 having a high thermal conductivity and the Ag or Ag alloy layer 8 exhibiting good characteristics, it is also possible to directly measure the thermal conductivity of each of them. The quality of heat conduction can be estimated using electrical resistance. 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. Volume resistivity and area resistivity are the usual 4
It can be measured by the probe method and is specified by JIS K 7194. This method provides much simpler and more reproducible data than actually measuring the thermal conductivity of the thin film itself.

In the present invention, preferable properties of the reflection / heat dissipation layer 2 and the Ag or Ag alloy layer 8 are volume resistivity of 20 nΩ · m or more and 150 nΩ · m or less, more preferably 20 nΩ · m or more, 100 nΩ · m. 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 sheet resistivity can be reduced by using a thick film having a thickness of more than 300 nm. However, according to the study by the present inventors, such a high volume resistivity is obtained. A sufficient heat dissipation effect could not be obtained even if only the sheet resistivity was lowered with the rate material. It is considered that the thick film increases the heat capacity per unit area. Further, such a thick film takes time to form a film and increases the material cost, which is not preferable from the viewpoint of manufacturing cost, and further, the microscopic flatness of the film surface is deteriorated. It is preferable to use a low volume resistivity material capable of obtaining an area resistivity of 0.2 or more and 0.9 Ω / □ or less at a film thickness of 300 nm or less, and most preferably 0.5 Ω / □. In the case of Ag or Ag alloy layer 8, the thickness is preferably 20 nm or less from the viewpoint of transmittance.

Regarding the multilayer structure of the reflection / heat dissipation layer 2 or the Ag or Ag alloy layer 8, a high volume resistivity material and a low volume resistivity material are combined to obtain a desired sheet resistivity with a desired film thickness. It is valid. 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, pure Al
It is also effective to obtain a desired volume resistivity by multilayering a thin film of 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 reflection and heat dissipation layer 2 is a multilayer reflection and heat dissipation layer composed of a plurality of metal films, and the total film thickness is 40 nm or more and 300 nm or less,
50% or more of the thickness of the multilayer reflection / heat dissipation layer has a volume resistivity of 20 n
It is preferable to use a metal thin film layer (may be a multilayer) of Ω · m or more and 150 nΩ · m or less.

Next, when a cover substrate 13 is provided as shown in FIG. 1 and an objective lens having a high NA is used,
Since the cover substrate 13 is required to have a thickness of 0.3 mm or less, more preferably 0.06 to 0.20 mm, it is preferable that the cover substrate 13 has a sheet shape. Materials include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin,
Examples thereof include polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin, and the like, and polycarbonate resin and acrylic resin, which are excellent in optical characteristics and cost, are preferable. Examples of the method for forming a thin substrate using the transparent sheet include a method in which the transparent sheet is attached via an ultraviolet curable resin or a transparent double-sided adhesive sheet. Alternatively, an ultraviolet curable resin may be applied onto the protective layer and cured to form a thin substrate.

[0059]

EXAMPLES The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the examples.

Example 1 With the layer structure shown in FIG. 3, a reflective heat dissipation layer 22 (AgCuPtPd), a first protective layer 23 (ZnSSiO ₂ ), and a first recording layer 24 (Ag ₅ In ₅ ) were formed on a polycarbonate substrate 21.
Sb ₆₅ Te ₂₅ ), the second protective layer 25 (ZnSSiO ₂ ),
Resin intermediate layer 26 (polycarbonate), third protective layer 27
(Be ₂ O ₃ ), Ag or Ag alloy layer 28 (AgCuP
tPd), fourth protective layer 29 (ZnSSiO ₂ ), second recording layer 30 (Ge ₅ Ag ₂ Sb ₇₀ Te ₂₃ ), fifth protective layer 31
(ZnSSiO ₂ ), the adhesive layer 32 (acrylic double-sided adhesive), and the cover substrate 33 (polycarbonate) were formed to prepare a phase change recording medium for evaluation. The layers other than the polycarbonate resin intermediate layer 26 and the acrylic double-sided adhesive layer 32 were formed by sequentially forming each layer from the substrate 21 side while controlling the thickness by a sputtering method.

The thickness of each constituent layer was controlled as follows. Substrate 21: 1.1 mm, reflective heat dissipation layer 2
2: 120 nm, first protective layer 23:10 nm, first recording layer 24:10 nm, second protective layer 25: 100 nm, resin intermediate layer 26:30 μm, third protective layer 27: 120 nm,
Ag or Ag alloy layer 28:10 nm, fourth protective layer 2
9:10 nm, second recording layer 30: 6 nm, fifth protective layer 3
1: 100 nm, adhesive layer 32: using acrylic double-sided adhesive, cover substrate 33:60 μm.

Example 2 The configuration and thickness of Example 1 were changed except that the material of the third protective layer 27 was changed from Be ₂ O ₃ to a mixed system composition of Al ₂ O ₃ and SiO _2. A phase change recording medium for evaluation was produced in exactly the same manner.

Example 3 The configuration and thickness of Example 1 were exactly the same as Example 1 except that the material of the third protective layer 27 was changed from Be ₂ O ₃ to a mixed system composition of MgO and SiO _2. Thus, a phase change recording medium for evaluation was produced.

Example 4 The structure and thickness of Example 1 were completely changed except that the material of the third protective layer 27 was changed from Be ₂ O ₃ to a mixed composition of In ₂ O ₃ and ZnO. A phase change recording medium for evaluation was prepared in the same manner.

Example 5 The configuration and thickness of Example 1 were changed except that the material of the third protective layer 27 was changed from Be ₂ O ₃ to In ₂ O ₃ , ZnO and SnO. In the same manner as above, a phase change recording medium for evaluation was prepared.

Comparative Example 1 A phase change for evaluation was made in the same manner as in Example 1 except that the material of the third protective layer 27 was changed from Be ₂ O ₃ to ZnSSiO _2. A mold recording medium was produced.

Table 1 shows the constituent materials of the respective layers of the evaluation phase change recording medium in Examples 1 to 5 and Comparative Example 1.

[0068]

[Table 1]

<Evaluation> Above Examples 1 to 5 and Comparative Example 1
The evaluation phase change recording medium manufactured in
Irradiate a focused light beam using an optical system with 2 nm and numerical aperture NA 0.85, linear velocity: 6 m / s, 0.130 μm / bi
Under the condition of t, initial jitter (Jitter), archival characteristics, and O / W characteristics were evaluated. The results are shown in Table 2.

[0070]

[Table 2]

Evaluation criteria are as follows. Archival property: Time (H) at which the increase in jitter (Jitter) becomes 20% or more when stored at 80 ° C. and 85% (RH). O / W characteristics: The number of overwrite (O / W) times (times) at which the increase in jitter due to overwrite (O / W) reached 20%.

As a result of the above evaluation test, the evaluation phase change recording media of Examples 1 to 5 according to the present invention have excellent archival characteristics (1000H to 2000H) and O / W characteristics (10000 times to 20000 times). ), The performance was 10 times or more as compared with the characteristics of 100 H (archival characteristics) and 1000 times (O / W characteristics) of the comparative example.

[0073]

According to the present invention, there is provided a layer structure in which at least a first recording constituent layer, a resin intermediate layer and a second recording constituent layer are provided on a substrate, and the first recording constituent layer is arranged in order from the substrate side. It comprises a reflection heat dissipation layer, a first protective layer, a first recording layer, and a second protective layer, and the second recording component layer is a third protective layer, an Ag or Ag alloy layer, and a fourth protective layer in this order from the resin intermediate layer side. Layer, a second recording layer, and a fifth protective layer, wherein the first recording layer and the second recording layer contain at least SbTe, and the linear expansion coefficient of the third protective layer is 3.0 × 10 ⁻⁶ or more. A phase that exhibits excellent O / W characteristics, archival characteristics, and high-density recording performance without noise such as jitter due to the structure of 10 × 10 ⁻⁶ and light transmittance of 80% or more. A variable recording medium is provided. Further, the component for forming the third protective layer of the present invention is Be ₂ O ₃ , or a mixed system composition of Al ₂ O ₃ and SiO ₂ , a mixed system composition of MgO and SiO ₂ , or In ₂ O ₃ . ZnO mixed system composition or In ₂ O ₃
Composition of ITO and SnO ₂ (ITO) or In ₂ O
_{By using} a mixed system composition of ₃ , ₃ , ZnO and SnO ₂ , it is possible to cope with the thermal volume change at the time of O / W, which results in good archival characteristics and high density with improved O / W characteristics. A phase change recording medium capable of recording is provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a layer structure showing an example for explaining a phase-change recording medium of the present invention.

FIG. 2 is a diagram showing the relationship between the linear expansion coefficient of the third protective layer 7 and the number of O / W of the second recording layer 10 in the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a layer structure of an evaluation phase change recording medium in an example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate 2 Reflective heat dissipation layer 3 First protective layer 4 First recording layer 5 Second protective layer 6 Resin intermediate layer 7 Third protective layer 8 Ag or Ag alloy layer 9 Fourth protective layer 10 Second recording layer 11 Fifth protection Layer 12 Adhesive Layer 13 Cover Substrate 21 Substrate (Polycarbonate) 22 Reflective Heat Dissipation Layer (AgCuPtPd) 23 First Protective Layer (ZnSSiO ₂ ) 24 First Recording Layer (Ag ₅ In ₅ Sb ₆₅ Te ₂₅ ) 25 Second Protective Layer (ZnSSiO) ₂ ) 26 resin intermediate layer (polycarbonate) 27 third protective layer (Be ₂ O ₃ ) 28 Ag or Ag alloy layer (AgCuPtPd) 29 fourth protective layer (ZnSSiO ₂ ) 30 second recording layer (Ge ₅ Ag ₂ Sb ₇₀₎ Te ₂₃₎ 31 fifth protective layer (ZnSSiO ₂₎ 32 adhesive layer (acrylic double-sided adhesive) 33 cover substrate (polycarbonate) 100 first recording structure layer 20 Second recording structure layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 7/24 538 G11B 7/24 538E

Claims (7)

[Claims] 1. A substrate is provided with at least a first recording component layer, a resin intermediate layer, and a second recording component layer in this order, and the first recording component layer comprises a reflection heat dissipation layer and a first recording component layer in that order from the substrate side. It is composed of a protective layer, a first recording layer and a second protective layer, and the second recording component layer is a third protective layer, an Ag or Ag alloy layer, a fourth protective layer and a second recording layer in this order from the resin intermediate layer side. A phase-change recording medium composed of a fifth protective layer, wherein the first recording layer and the second recording layer contain at least SbTe, and the linear expansion coefficient of the third protective layer is 3.0 × 10. ^-6 to 10 x 10 ^-6
And a light transmittance of 80% or more. 2. The phase change recording medium according to claim 1, wherein the component forming the third protective layer is Be ₂ O ₃ . 3. The phase change recording medium according to claim 1, wherein the component for forming the third protective layer is a mixed system composition of Al ₂ O ₃ and SiO ₂ . 4. The components for forming the third protective layer are MgO and S.
_2. A mixed system composition with iO.sub.2.
The described phase change recording medium. 5. The composition for forming the third protective layer is a mixed composition of In ₂ O ₃ and ZnO.
The described phase change recording medium. 6. The phase change recording medium according to claim 1, wherein the component forming the third protective layer is a mixed system composition of In ₂ O ₃ and SnO ₂ . 7. The phase-change recording medium according to claim 1, wherein the component forming the third protective layer is a mixed system composition of In ₂ O ₃ , ZnO and SnO ₂ .