JP2003115131A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concrete configuration when two optical recording media are layered and to specify conditions that an optical recording medium is manufactured at low costs and satisfactorily attached to a driving device in an optical recording medium for high density recording having a phase transition type recording layer. SOLUTION: In the optical recording medium utilizing a phase transition phenomenon and constituted of a first protective layer 2, a recording layer, a second protective layer 4 and a reflective heat dissipation layer 5 layered in this order on a substrate 1 having grooves formed thereon, recording or erasure of recording pit information is performed at the recording layer of the groove part. The first and the second protective layers consists of a mixture of ZnS and SiO2 , the recording layer has Ge, Sb and Te as main constituent elements and the reflective heat dissipation layer 5 consists of Al alloy. The two optical recording media are layered via a resin adhesive layer therebetween, the grooves opposed to each other of the mutual substrates are shifted by one row or more and the two optical recording media are layered and stuck to each other with the shift amount within the range where the two optical recording media can be attached to the driving device for driving the media.

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 for high density recording such as D having a phase change recording layer.

[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. CD in recent years
As a medium compatible with, a phase change type rewritable compact disc (CD-RW, CD-Rewrita)
ble) 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 a recorded information signal by utilizing the difference in reflectance and the change in phase difference caused by the difference in refractive index between an amorphous state and a crystalline state. A typical phase change medium has a lower protective layer on the substrate,
It has a structure in which a phase-change recording layer, an upper protective layer, and a reflective layer are provided, and by utilizing multiple interference of these layers, it is possible to control the reflectance difference and the phase difference and to make them 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 CD-RW and rewritable DVD. Includes overwrite recording in which recording and erasing are performed simultaneously. For recording information using phase change, a crystalline state, 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 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, GeTe—Sb ₂ Te ₃ pseudo-binary alloy containing GeSbTe as a main component, InTe—Sb ₂
In ₃ SbTe based on Te ₃ pseudo binary alloy, S
b _{0 . 7} Te _0.3 AgInS containing eutectic as a main component
Examples include bTe alloys and GeSnTe alloys. this house,
_GeTe-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
Compositions near intermetallic compounds such as Sb 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. For this reason, a pseudo binary alloy system or a composition in the vicinity of an intermetallic compound has been attracting attention as a recording layer exhibiting practical overwrite characteristics (Reference Jpn. J. Appl. Phys., Vol.69).
(1991), p2849, or SPIE, Vol. 2514 (1995), pp29
4-301 etc.).

Further, it has been conventionally reported that the ternary composition of GeSbTe, or the composition of the recording layer containing the ternary composition as a matrix and containing an additive element (JP-A-61-2).
58787, JP-A-62-53886, JP-A-62-152786, JP-A-1-63195.
Japanese Patent Laid-Open No. 1-211249 and Japanese Patent Laid-Open No. 1-212
77338). However, application of the material having such a composition to an optical recording medium for high-density recording such as a rewritable DVD has just begun development and there are many problems to be solved. One of the problems is to increase the capacity, and there is an idea of stacking two optical recording media to double the capacity. However, how to stack two optical recording media with high accuracy has not been studied yet.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the circumstances as described above, and firstly, its purpose is to provide a high density recording medium having a phase change recording layer such as a rewritable DVD. In an optical recording medium for recording, in order to increase the recording capacity, it is to clarify a specific configuration when two optical recording media are stacked. Secondly, it is necessary to clarify the conditions under which an optical recording medium obtained by laminating and adhering two such optical recording media can be manufactured at low cost and can be favorably attached to a drive device. Thirdly, it is to propose another example of the specific configuration of the optical recording medium in which two such optical recording media are laminated and adhered.

[0009]

The above-mentioned problems are solved by the present invention.
(1) "Phase transition between crystalline and amorphous due to light irradiation
In an optical recording medium utilizing the
On the formed substrate, the first protective layer, the recording layer, the second protective layer
Layer and a reflective heat dissipation layer are laminated in this order, and the groove
The recording bit information is recorded or erased in the recording layer of
The optical recording medium to be removed, wherein the first and second protective layers are
ZnS and SiO_TwoAnd the recording layer is G
The reflection and heat dissipation layer containing e, Sb, and Te as main constituent elements
Is made of Al alloy and has a resin adhesive layer between the optical recording media.
Via the first protective layer, the recording layer, the second protective layer,
Two sheets are stacked with the surfaces with the reflective heat dissipation layer facing each other.
Layers and make sure that there are no more than
And driving the optical recording medium in which the two recording layers are stacked.
Stacked connection as a shift amount within the range that can be installed in live equipment
Optical recording medium characterized by being worn ”, (2)
The load amount is set at the center of each of the two optical recording media.
It is characterized in that it is the amount of deviation of the center axis of the carved circular hole.
The optical recording medium according to the above item (1),
Utilizing the phase transition phenomenon of crystalline and amorphous by irradiation
In the optical recording medium, the optical recording medium has a groove-formed substrate.
On the plate, the first protective layer, the recording layer, the second protective layer, the reflective layer
The thermal layer is laminated in this order, and the recording layer of the groove is formed.
Optical recording for recording or erasing recorded bit information
A recording medium, wherein the first and second protective layers are ZnS and S
iO _TwoThe recording layer is made of Ge, Sb, T
The main constituent element is e, and the reflection / heat dissipation layer is made of an Al alloy.
And a resin adhesive layer is interposed between the recording medium and
Form the first protective layer, recording layer, second protective layer, and reflective heat dissipation layer.
When the two surfaces are stacked with the surfaces made facing each other
The grooves facing each other are offset by one or more rows, and
For a drive device that drives the optical recording medium in which two sheets are stacked.
Installed and the writing pickup of the drive device added
It is a special feature that they are laminated and bonded as a shift amount within the range that can comply.
Optical recording medium.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic sectional view of a recording portion of an optical recording medium according to the present invention, in which a substrate (1) / first protective layer (2) / recording layer ( 3) / second protective layer (4) / reflection heat dissipation layer (5). In addition, an ultraviolet ray or a thermosetting resin is coated thereon (on the reflection / heat radiation layer (5)) (protective coating layer (6)) (this will be described later).

The order of the layers as shown in FIG. 1 is suitable for irradiating the recording layer with a focused light beam for recording and reproduction, for example, a laser beam through the transparent substrate. First, the substrate (1) will be described. For the substrate (1), transparent resin such as polycarbonate, acryl, polyolefin, or transparent glass can be used. 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. The substrate (1) is provided with a groove for guiding the recording / reproducing light. As shown in FIG. 1, the groove portion is called a groove portion and the portion next to it is called a land portion. The groove portions are formed with a pitch of 0.8 μm or less (for example, 0.74 μm), and recording bit information is added to a recording layer (described later) of the groove portions to write / erase / reproduce the recording bit information. (Reading) is performed. The cross-sectional shape of the groove portion (land portion / groove portion) does not necessarily have to be a geometrically rectangular or trapezoidal groove.
The groove may be formed optically by forming a waveguide like one having a different refractive index by ion implantation or the like.

Next, the recording layer (3) of the present invention will be described. The recording layer (3) of the optical recording medium of the present invention is a phase change type recording layer, and its thickness is generally 5 nm to 100 n.
A range of m is preferred. When 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 that is compatible with a read-only disc such as a DVD, and for high-density recording in which the shortest mark length is 0.5 μm or less, 5 nm or more and 25 nm or less is preferable. 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 the thickness is more than 25 nm, the heat capacity becomes large, the recording sensitivity becomes poor, and the crystal growth becomes three-dimensional, so that the edges of the amorphous marks tend to be disturbed and the jitter tends to increase. 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.

In the sputtering film forming method, the density of the recording layer is set by lowering the pressure of the sputtering gas (rare gas such as Ar) at the time of forming the film, or by disposing the substrate close to the front surface of the target. It is necessary to increase the amount of high-energy Ar that is irradiated to the. High-energy Ar means that Ar ions irradiated on the target for sputtering are partially repelled and reach the substrate side, or Ar ions in plasma are 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, when the amount of Ar is large, high-energy Ar irradiation is intense and the density is high, but the amount of A incorporated in the film is large.
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 Ge, Sb, T
It is composed of a thin film whose main component is an alloy containing e as a main constituent element. That is, the composition ratios of Ge, Sb, and Te in the recording layer are 1 at% or more and 5 at% or less, 65 at% or more and 85 at% or less, and 15 at% or more and 30 at% or less, respectively. Other elements may be added to the recording layer, if necessary, up to a total of about 10 atom%. 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 over 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 Al, Ga and In in an amount of 8 atomic% or less not only raises the crystallization temperature but also reduces jitter and improves 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 especially when it is used 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.

The recording layer (3) of the recording medium of the present invention.
In general, the state after film formation is amorphous. Therefore,
After the film formation, it is necessary to crystallize the entire surface of the recording layer to an initialized state (unrecorded state). As the initialization method, initialization by solid phase annealing is possible, but initialization by melt recrystallization in which the recording layer is once melted and gradually cooled during resolidification to be crystallized is desirable. This recording layer has almost no crystal growth nuclei immediately after film formation, and it is difficult to crystallize in the solid phase.However, by melt recrystallization, a small number of crystal nuclei are formed and then melted. , The crystal growth is the main, and the recrystallization proceeds at high speed.

Further, in the recording layer of the present invention, the crystal due to the melting recrystallization and the crystal due to the annealing in the solid phase have different reflectances, so that if mixed, it causes 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, a high-power semiconductor laser beam with a wavelength of about 600 to 1000 nm is used, with a major axis of 100 to 300 μm and a minor axis of 1 μm.
Focus and irradiate to ~ 3μm, the short axis direction as the scanning axis,
It is desirable to scan at a linear velocity of 1 to 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. When 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 in which it is 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. 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) / {(Rini + Rcry) / 2} means that the difference in reflectance between the two is 20% or less. Usually, the difference in reflectance is 20% only by solid phase crystallization such as annealing.
Greater than

As shown in FIG. 1, the recording layer of the present invention has a structure in which it is sandwiched between the first protective layer (2) and the second protective layer (4), and the substrate (1 ) Provided on the surface (groove forming surface). Here, the first protective layer (2) is mainly effective in preventing the deformation of the surface of the substrate (1) due to a high temperature during recording. Further, the second protective layer (4) prevents mutual diffusion of the recording layer (3) and the reflection heat dissipation layer (5), suppresses the deformation of the recording layer (3), and efficiently transfers to the reflection heat dissipation layer (5). It also has the function of releasing heat.

The material of the protective layers (2) and (4) is determined by taking into consideration the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion and the like. In general, metal or semiconductor oxides, sulfides, nitrides, carbides and fluorides such as Ca, Mg, and Li having high transparency and high melting point can be used. As a result of investigating the materials, it is considered that the mixture of ZnS and SiO ₂ is the most preferable in view of the above viewpoint and the compatibility with the material constituting the recording layer (3) of the present invention. Not limited to this material, the above oxides, sulfides, nitrides, carbides, and fluorides do not necessarily have to have a stoichiometric composition, and the composition is controlled or mixed to control the refractive index and the like. It is also effective to use.

The function of the protective layer and the like 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 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 film thickness of the second protective layer (4) is set to 5 nm or more and 30 nm or less. 5
If the thickness is less than 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 30n
When it is thicker than m, the temperature difference between the recording side and the reflecting layer side of the second protective layer becomes large at the time of recording, 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. Become. 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 material of the present invention as described above is used, low jitter can be realized in high density recording with a shortest mark length of 0.5 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 700 nm or less) is used, it is necessary to pay more attention 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 for high erasing ratio and erasing. It has been found to be important for ensuring a wide 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 particularly low thermal conductivity is 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 the erasing power margin can be improved by forming the reflective heat dissipation layer (5) provided thereon with a material having particularly high thermal conductivity. According to the study, in order to exert 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 (recording beam scanning direction) It is preferable to use a layer structure capable of flattening the temperature distribution in the vertical direction).

By properly designing the layer structure of the optical recording medium, the inventors of the present invention flatten the temperature distribution in the cross-track direction in the medium, thereby melting and re-amorphizing. Instead, the width that can be recrystallized is expanded, and the erasing rate and the erasing power margin are expanded. on the other hand,
It was found that the temperature distribution in the recording layer becomes flat by promoting the heat dissipation from the recording layer to the reflective heat dissipation layer having an extremely high thermal conductivity through the second protective layer having a low thermal conductivity and a very thin thickness. . Although the heat dissipation effect is promoted even if the thermal conductivity of the second protective layer is increased, if the heat dissipation is promoted too much, the irradiation power required for recording increases, that is, the recording sensitivity decreases significantly.

In the present invention, a thin second layer having a low thermal conductivity is used.
It is preferable to use the above protective layer. By using the thin second protective layer having a low thermal conductivity, several nsec to several tens of nanoseconds at the start of recording power irradiation. In nsec, heat conduction from the recording layer to the reflective layer can be delayed in time, and heat dissipation to the reflective layer can be promoted thereafter, so that the recording sensitivity is not unnecessarily lowered by heat dissipation. Conventionally _{known, SiO 2, Ta 2 O 5} , Al 2 O 3, Al
The protective layer material containing N, SiN or the like as a main component has a too high thermal conductivity and is not preferable as the second protective layer (4) of the optical recording medium of the present invention by itself.

On the other hand, the heat radiation in the reflection heat radiation layer (5) is
This can be achieved by increasing the thickness of the reflective heat dissipation layer (5), but when the thickness of the reflective heat dissipation layer (5) exceeds 300 nm, the heat conduction in the film thickness direction becomes more remarkable than in the film surface direction of the recording layer (3). Becomes
The effect of improving the temperature distribution in the film surface direction cannot be obtained. Further, the heat capacity of the reflective heat dissipation layer (5) itself becomes large, and it takes time to cool the reflective heat dissipation layer (5) and eventually the recording layer (3), which hinders the formation of amorphous marks. Most preferably, the reflective heat dissipation layer (5) having a high thermal conductivity is thinly provided to selectively promote heat dissipation in the lateral direction. The quenching structure used conventionally pays attention only to the one-dimensional escape of heat in the film thickness direction, and from the recording layer (3) to the reflection heat dissipation layer (5).
It was intended only to quickly release heat, and no sufficient attention was paid to the flattening of the temperature distribution in the plane direction.

Incidentally, 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 (3) of the present invention, is a conventional GeTe-Sb.
It is more effective than the ₂ Te ₃ recording layer. This is because, in the recording layer (3) 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 (4) has a low thermal conductivity, but the standard is 1 × 10 ⁻³ pJ / (μm · K · nsec). However, it is difficult to directly measure the thermal conductivity of such a low thermal conductivity material in a thin film state, and instead, a guide can be obtained from thermal simulation and actual measurement results of recording sensitivity. Examples of the material for the second protective layer having a low thermal conductivity that gives favorable results include ZnS and Zn.
A composite dielectric containing at least one of O, TaS _{2, and} rare earth sulfides in an amount of 50 mol% to 90 mol% and a heat-resistant compound having a melting point or a decomposition point of 1000 ° C. or more 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, ZnS, ZnO
Alternatively, the composition range of the rare earth sulfide is 70 to 90 mol.
It is desirable to set it as%. Examples of the heat-resistant compound material having a melting point or a decomposition point of 1000 ° C. or higher to be mixed with these include Mg, Ca, Sr, Y, La, Ce, Ho, Er,
Yb, Ti, Zr, Hf, V, Nb, Ta, Zn, A
l, Si, Ge, Pb and other oxides, nitrides, carbides and C
Fluorides such as a, Mg and Li can be used.

Particularly, SiO ₂ is desirable as a material to be mixed with ZnS, and the present invention considers that this combination is optimal. If the thickness of the second protective layer (4) 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 1 when the wavelength of the recording laser light is 600 to 700 nm.
5 nm to 25 nm is preferable, and the wavelength is 350 to 600 n.
m is preferably 5 to 20 nm, more preferably 5 to 1
It is 5 nm.

In the present invention, both the first and second protective layers are made of ZnS and SiO ₂ as described above. However, if the same material is used, the manufacturing cost can be reduced. Is also advantageous.

Next, the reflection / heat dissipation layer (5) will be described. In the present invention, it has a very high thermal conductivity of 300 nm.
The following thin reflective heat dissipation layer (5) 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 heat dissipation layer (5) can be directly measured in order to define the high thermal conductivity reflective heat dissipation layer (5) exhibiting good characteristics.
The quality of the heat conduction can be estimated by using the electric 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 the measurement region.
Volume resistivity and area resistivity can be measured by the usual 4 probe method,
It 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.

Reflective heat dissipation layer (5) preferred in the present invention
The characteristic is that the volume resistivity is 20 nΩ · m or more 150
It is 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 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 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. Preferably, the area resistivity is 0.2 or more and 0.9 Ω / □ at a film thickness of 300 nm or less.
A low volume resistivity material is used such that:
0.5Ω / □ is the most preferable.

Materials suitable for the present invention are as follows. For example, it is an Al-Cu alloy containing 0.3% by weight or more and 5.0% by weight or less of Cu. Especially ZnS and Si
_Second protective layer containing a mixture of O ₂ as a main component (4)
On the other hand, an Al-Cu based alloy containing Cu in an amount of 0.5% by weight or more and 4.0% by weight or less is desirable as a reflection / radiation layer satisfying all of corrosion resistance, adhesion, and high thermal conductivity in good balance.

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% is also effective. Furthermore, A
l, Ta, Ti, Co, Cr, Si, Sc, Hf, P
0.2 atomic% of d, Pt, Mg, Zr, Mo, or Mn
The Al alloy containing 2 atom% or less has a volume resistivity increased in proportion to the concentration of the additional element, and has improved hillock resistance, and should be used in consideration of durability, volume resistivity, film formation rate, and the like. it can. For Al alloys, the amount of added impurities is 0.2
If it is less than atomic%, 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.

For the second protective layer (4) whose main component is a mixture of ZnS and SiO ₂ , Ta is 0.
An AlTa alloy with a content of 5 atomic% or more and 0.8 atomic% or less is desirable as a reflective heat dissipation layer that satisfies all of corrosion resistance, adhesion, and high thermal conductivity in a well-balanced manner. Further, in the case of Ta, addition of only 0.5 atomic% of pure Al or Al-Mg-S
Compared with i alloy, the film formation rate during sputtering is 3 ~
It is possible to obtain a preferable effect in manufacturing that the amount is increased by 40%.

When the above Al alloy is used as the reflection / heat dissipation 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, and the heat capacity of the reflection / heat dissipation layer itself is large, which rather slows the cooling rate of the recording layer. 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 reflection / heat dissipation layer, the preferable film thickness is 30 nm or more and 200 n or less.
m or less. If it is less than 30 nm, the heat dissipation effect is insufficient even with pure Ag. When the thickness exceeds 200 nm, heat escapes in the vertical direction from the horizontal direction, does not contribute to the improvement of the heat distribution in the horizontal direction, and an unnecessary thick film reduces the productivity. In addition, the microscopic flatness of the film surface also deteriorates.

The inventors of the present invention added Ag, an additive element to the above Al.
It has been confirmed that the volume resistivity of the element added to the element 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 heat dissipation layer 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 atoms. It must be less than or equal to%. For this reason, it is desirable that the ultimate vacuum of the process chamber is 1 × 10 ⁻³ Pa or less. In addition, if the film is formed at an ultimate vacuum degree lower than 10 ⁻⁴ Pa, the film formation rate is 1 nm / sec or more,
It is desirable to prevent impurities from being taken in, preferably at 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. 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 also depends on the manufacturing method of the alloy target used for sputtering and the sputtering gas (Ar, Ne, Xe, etc.). As described above, the volume resistivity in a thin film state is not determined only by the metal material and 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. The optimum composition is determined in consideration.

It is also effective to make the reflection and heat dissipation layer multi-layered in order to obtain higher heat conduction and higher reliability. At this time,
At least one layer substantially controls the heat radiation effect as the low volume resistivity material having a film thickness of 50% or more of the total reflection heat radiation layer thickness, and the other layers have corrosion resistance, adhesion with the protective layer, and hillock resistance. Configured to contribute to the improvement of. More specifically, A, which has the highest thermal conductivity and the lowest volume resistivity among metals,
g 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, Ag and Ag are used as the low volume resistivity material.
It is also effective to use an alloy and to provide an alloy layer containing Al as a main component between 1 nm and 100 nm inclusive as an interface layer between the alloy and 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, for example, T
a, Ti, Co, Cr, Si, Sc, Hf, Pd, P
t, Mg, Zr, Mo, or Mn is 0.2 atomic% or more 2
An Al alloy containing at most atomic% can be used. If the thickness of the interface layer is less than 1 nm, the protective effect is insufficient, and if it exceeds 100 nm, the heat dissipation effect is sacrificed. The use of the interface layer is particularly effective when the reflection / heat dissipation 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.

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. 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 is impaired, which is not preferable. The multilayered reflection / heat dissipation 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. The adjustment of the volume resistivity by alloying can simplify the sputtering process by using the alloy target, but it also increases the manufacturing cost of the target and eventually the raw material ratio of the medium. Therefore, pure Al and pure Ag
It is also effective to obtain a desired volume resistivity by forming a multi-layer of the above thin film and the above 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 / heat dissipation layer is a multilayer reflection / heat dissipation layer composed of a plurality of metal films, the total thickness is 40 nm or more and 300 nm or less, and 50% or more of the thickness of the multilayer reflection / heat dissipation layer is 20 nΩ · m or more in volume resistivity.
Metal thin film layer of 50 nΩ · m or less (may be multi-layer)
Is preferred.

FIG. 2 shows one completed image of the optical recording medium having the above-mentioned structure, in which an ultraviolet ray or a thermosetting resin (protective coating layer (6)) is provided on the reflective heat radiation layer (5). The protective substrate (7) is attached. The protective coat layer (6) is formed by applying the above resin by spin coating or the like, and the protective substrate (7) is a transparent resin such as polycarbonate, acryl, or polyolefin, similar to the substrate (1).
Alternatively, transparent glass can be used. Above all,
Polycarbonate resin is inexpensive and most preferable.

FIG. 3 shows that, in place of the protective substrate (7) of FIG. 2, another optical recording medium is attached via a protective coat layer (6) in a mirror image relationship with the optical recording medium below. It is a thing. Corresponding to the substrate (1), the first protective layer (2), the recording layer (3), the second protective layer (4), and the reflective heat dissipation layer (5) of the lower optical recording medium, the substrate (1 ' ), The first protective layer (2 ′), the recording layer (3 ′), the second protective layer (4 ′), and the reflection / heat dissipation layer (5 ′), and the material layers have the same thickness. By doing so, not only can the optical recording medium be protected, but the recording capacity can be doubled.

Next, a method of recording information on the optical recording medium of the present invention will be described. When recording the information of which the mark length is modulated by irradiating the optical recording medium of the present invention with a plurality of recording mark lengths, assuming that the time length of one recording mark is nT (T is a reference clock). The period is 25 ns or less, n is a natural number of 2 or more.), And the temporal length nT of the recording mark is

[0050]

## EQU1 ## 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 (m is the pulse division number. Σ _i (α _i + β _i ) + η ₁ + η
₂ = n. α _i (1 ≦ i ≦ m) is a real number greater than 0, β _i (1 ≦ i ≦ m−1) is a real number greater than 0, and β _m is a real number greater than or equal to 0. Each of η ₁ and η ₂ is a real number of −2 or more and 2 or less. ) Order, and α _i
Within the time period of T (1 ≦ i ≦ m), the recording power Pwi
Of the recording light of the bias power Pbi satisfying Pbi <Pwi and Pbi <Pwi _{+ 1} within a time period of β _i T (1 ≦ i ≦ m−1). Regarding the temporal length, the pulse division number m is set to 2 or more, and n / m ≧ 1.25 is satisfied for the temporal length of all recording marks.

By the way, as described above, in the present invention, the substrate (1) is provided with the groove having the pitch of 0.8 μm or less (for example, 0.74 μm) for guiding the laser beam for recording and writing, and the groove forming surface is formed. The recording layer (3) and other layers are provided. Then, two optical recording media are made to face each other with their surfaces having grooves and recording layers (3) formed thereon, and are laminated and bonded in a mirror image relationship to realize an optical recording medium with double the recording capacity. FIG. 3 shows this. That is, since the two optical recording media are laminated and joined so as to have a mirror image relationship, the positions of the grooves and the like (lands and grooves) are completely the same.

This does not cause any problem in terms of performance as a recording medium for obtaining a capacity twice as large as that of the present invention, but on the other hand, the land portion and groove portion of each other with such high precision are provided. When they are laminated and adhered with high accuracy so that they have a mirror image relationship, the manufacturing cost thereof is very high. This is because a highly accurate jig and tool is required for alignment during stacking, the adhesive itself has fluidity, and when it cures, it temporarily generates heat and fluidity. Is increased, which may cause misalignment of highly accurate alignment during stacking. In other words, very accurate positioning jigs and adhesive jigs are required.

FIG. 4 schematically shows such a two-layer laminated type optical recording medium to which the present invention is applied and its drive device. In the figure, (8) is a two-layer laminated optical recording medium, (8-1) is a first optical recording medium, and (8-2) is a second optical recording medium.
Optical recording medium, (9) is a circular opening formed in the central portion of the optical recording medium, and (10) is a laser beam irradiating land and groove portions of such an optical recording medium for optical access. However, a pickup unit for recording the recording bit information, (11) is a rotating shaft for rotating the optical recording medium, (1)
2) shows a drive device.

FIG. 4A shows a two-layer laminated optical recording medium (8).
Is not attached to the drive device (12),
In FIG. 4 (b), the circular opening (9) formed in the central portion of the optical recording medium is inserted into the rotating shaft (11), and the two-layer laminated optical recording medium (8) is mounted in the drive device (12). It shows the state. The pickup unit (10) records the recording bit information in the groove portion while moving in the direction of the arrow in the figure.

By the way, the present inventor has conducted research and development of an optical recording medium having a double capacity by stacking two sheets as described above.
The above two upper and lower optical recording media (8-1), (8-
I noticed that there was something while I was trying to stack and adhere 2) with high precision and making the upper and lower grooves completely match. That is, in the case of actually recording the recording bit information by the drive device as shown in FIG. 4 in the optical recording medium in which two optical recording media such as the present invention are laminated and adhered, recording is performed on one side each. The usage is considered to be general. That is, to explain with reference to the example of FIG. 4, when the recording bit information is recorded on the optical recording medium (8-2), and when it is completed, the optical recording medium (8) is turned upside down and then It is considered that the optical recording medium (8-1) is generally used for recording recording bit information. Alternatively, although the drive device is slightly expensive, the pickup unit (10) shown in FIG. 4 is provided above and below the optical recording medium (8) and the optical recording medium (8) is not turned upside down. Conceivable.

In any case, however, the operation of recording the recording bit information is performed with high accuracy by the pickup unit (10) (or another pickup unit not shown), so that tracking error, recording error, etc. are prevented. Therefore, it has been found that it is not always necessary to completely match the upper and lower groove portions of the upper and lower optical recording media (8-1) and (8-2). Instead, I realized that it is an important issue to be able to install the two-layer laminated optical recording medium (8) of the present invention in the drive device (12). That is, the two-layer laminated optical recording medium (8) according to the present invention can be installed in the drive device (12), and if the optical recording medium can be rotated by the rotation shaft (11), the tracking control pickup unit (10) can be used. Since recording bit information can be freely recorded, two upper and lower optical recording media (8-
1) and (8-2) were laminated and adhered with high precision so that the upper and lower groove portions were not completely aligned. FIG. 5 is a partial cross-sectional view of the double-layered optical recording medium (8) of the present invention, in which each of the first optical recording medium (8-1) and the second optical recording medium (8-2) is separated from each other. It was manufactured so that the groove portions (lands and grooves) of (1) do not match.

FIG. 6 shows an example in which the circular openings of the first optical recording medium (8-1) and the second optical recording medium (8-2) are displaced and laminated and bonded. The center points of the circular opening (9-1) of the first optical recording medium and the circular opening (9-2) of the second optical recording medium are offset by ΔX in the X direction and ΔY in the Y direction and laminated and bonded. Is. In this case, the diameters (D1) and (D1) of the circular openings (9-1) and (9-2), respectively.
2) are formed to be equal (= Φ15m
m) so that the circular aperture (9) of the two-layer laminated optical recording medium (8)
Is (ΔX ² + ΔY) from (D1) (or (D2))
^The value becomes smaller by the value of the square root of ² ), which is regarded as the diameter of the substantially circular opening (9) of the two-layer laminated optical recording medium 8. The diameter of the substantially circular opening (9) of the two-layer laminated optical recording medium (8) is smaller than the diameter of the rotation shaft (11) of the drive device (12) ( The amount of deviation between the center points of 9-1) and (9-2) is set.

In the present invention, this shift amount is at least the first optical recording medium (8-1) and the second optical recording medium (8-
In 2), the grooves are bonded to each other so that the grooves facing each other are offset by one or more rows. That is, they are laminated and bonded so as to be displaced by one pitch or more of the groove row for recording the recording bit information. Specifically, it is obtained by utilizing the property that the adhesive exhibits fluidity when the adhesive is cured in the bonding step. Further, the upper limit of the amount of deviation is set within a range in which such a double-layered optical recording medium (8) can be installed in the drive device (12). Specifically, the diameter of the substantially circular opening (9) of the two-layer laminated optical recording medium (8) is substantially the same as the diameter of the rotating shaft (11) of the drive device (12), but Inner wall of rotating circular opening (9) and rotating shaft (11)
The outer wall of the device has an appropriate friction, the two-layer laminated optical recording medium (8) is fixed to the drive device (12), and the two-layer laminated optical recording medium (8) is rotated by the rotation shaft (11). On the other hand, being able to rotate at the same number of rotations without slipping means that it can be installed.

Another important point is that, as shown in FIG. 4B, the pickup (10) moving in the arrow direction can perform focusing, tracking and tracking. That is, in order to reduce the manufacturing cost, the amount of misalignment between the first optical recording medium (8-1) and the second optical recording medium (8-2) is made as large as possible, and a rough structure is obtained. The two-layer laminated optical recording medium (8) is used, but by setting the upper limit of the shift amount within the range that the pickup (10) can follow, both cost reduction and satisfactory performance can be realized. Of.

[0060]

As is apparent from the detailed and specific description above, according to claim 1 of the present invention, in such an optical recording medium, a groove is formed in a substrate and a recording layer or the like is formed thereon. The two surfaces are laminated so that they face each other, and the opposing grooves of the substrates are offset by at least one row, and the optical recording medium having the two laminated layers is within a range that can be installed in a drive device for driving. Since the layers are bonded by laminating as a shift amount, it is possible to realize a capacity double that of a normal case. In addition, the amount of positional deviation that occurs when two sheets are laminated and adhered to each other is set to one or more rows of grooves facing each other, and the optical disc can be installed in a drive device that drives the two laminated optical recording media. Since the amount of shift is within the range, it is possible to install it in the drive device satisfactorily, and since the allowable range of positional deviation is loose and clear,
It becomes possible to realize such an optical recording medium in which two layers are bonded together at low cost. Further, according to claim 2 of the present invention,
In such an optical recording medium, the shift amount of the two optical recording media is set within the range of the shift amount of the central axis of the circular hole provided at the center of each of the two optical recording media. In addition to the first effect, since such an optical recording medium having two layers laminated and adhered can be inserted into the rotary shaft portion of the drive device without force, the user can forcefully insert the rotary shaft portion of the drive device or the optical recording medium. The inner wall of the hole of the recording medium may be damaged, or the entire drive unit may be damaged.
There is no accident that the optical recording medium itself is deformed or damaged. Furthermore, according to claim 3 of the present invention, in such an optical recording medium, two grooves are formed on the substrate, and the surfaces on which the recording layer and the like are formed face each other and are laminated together. Since the grooves facing each other on the substrate are displaced by one or more rows, and the two optical recording media that are laminated are laminated and bonded to each other within a shift amount that can be set in a drive device to be driven,
Double the capacity can be realized. In addition, when the two sheets are laminated and bonded to each other, the positional deviation amount is one row or more of the grooves facing each other, and when the two optical recording media are laminated and installed in a drive device. In addition, since the lamination adhesion is performed as a shift amount within a range that can be followed by the writing pickup of the drive device, the positional deviation accuracy at the time of adhesion is not so severe, and such optical recording with two lamination adhesion at low cost. You will be able to make media. Further, since the amount of deviation is within the range that the writing pickup of the drive device can follow, there is no problem in terms of function.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view for explaining a layer structure such as a recording layer of an optical recording medium applied to the present invention.

FIG. 2 is a partial cross-sectional view for explaining a case where the present invention is actually completed.

FIG. 3 is a partial cross-sectional view for explaining another configuration example when the present invention is actually completed.

FIG. 4 is a diagram schematically showing a two-layer laminated optical recording medium and a drive device thereof to which the present invention is applied.

FIG. 5 is a partial sectional view of a double-layered optical recording medium (8) of the present invention.

FIG. 6 is a diagram showing an example in which circular openings of the first optical recording medium (8-1) and the second optical recording medium (8-2) are shifted and laminated and bonded.

[Explanation of symbols]

1 substrate 1'substrate 2 First protective layer 2'first protective layer 3 recording layers 3 '... recording layer 4 Second protective layer 4'second protective layer 5 Reflective heat dissipation layer 5'Reflective heat dissipation layer 6 Protective coating layer 7 Protective board 8 Two-layer laminated optical recording medium 8-1 First optical recording medium 8-2 Second optical recording medium 9 circular openings 9-1 Circular opening 9-2 circular opening 10 pickup unit 11 rotation axis 12 Drive device D-1 diameter D-2 diameter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 7/24 538 G11B 7/24 538E (72) Inventor Tsuji Abe 1-3, Nakamagome, Ota-ku, Tokyo No. 6 In Ricoh Company (72) Inventor Yoshiyuki Kageyama 1-3-6 Nakamagome, Ota-ku, Tokyo In-house Ricoh Company (72) Kazunori Ito 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Within Ricoh Company (72) Inventor Michiaki Shinozuka 1-3-6 Nakamagome, Ota-ku, Tokyo F-terms within Ricoh Company, Ltd. (reference) 5D029 JA01 JB13 LA14 LA15 MA13 RA27

Claims (3)

[Claims] 1. An optical recording medium utilizing a crystal-amorphous phase transition phenomenon by light irradiation, wherein the optical recording medium comprises a first protective layer, a recording layer, and a second protective layer on a grooved substrate. An optical recording medium having a structure in which a recording layer and a reflection heat dissipation layer are laminated in this order, and recording or erasing recording bit information in the recording layer of the groove portion.
Of the protective layer is made of a mixture of ZnS and SiO ₂ , the recording layer has Ge, Sb, and Te as main constituent elements, the reflective heat dissipation layer is made of an Al alloy, and a resin adhesive layer is interposed between the optical recording medium. Then, the two surfaces on which the first protective layer, the recording layer, the second protective layer, and the reflection / heat dissipation layer are formed face each other, and two sheets are laminated, and the opposing grooves of the substrates are formed into one.
An optical recording medium, which is shifted by more than one row and is laminated and bonded so that the amount of shift is within a range that can be set in a drive device for driving the optical recording medium having the two laminated layers. 2. The optical recording according to claim 1, wherein the shift amount is a shift amount of a central axis of a circular hole provided at the center of each of the two optical recording media. Medium. 3. An optical recording medium utilizing a crystal-amorphous phase transition phenomenon by light irradiation, wherein the optical recording medium comprises a first protective layer, a recording layer and a second protective layer on a substrate having a groove formed therein. An optical recording medium having a structure in which a recording layer and a reflection heat dissipation layer are laminated in this order, and recording or erasing recording bit information in the recording layer of the groove portion.
Of the protective layer is made of a mixture of ZnS and SiO ₂ , the recording layer has Ge, Sb, and Te as main constituent elements, the reflective heat dissipation layer is made of an Al alloy, and the recording medium has a resin adhesive layer interposed therebetween. And stacking two sheets with the surfaces on which the first protective layer, the recording layer, the second protective layer, and the reflection / heat dissipation layer are formed facing each other, and displacing the grooves facing each other in one or more rows, and An optical recording medium, which is installed in a drive device for driving the optical recording medium having the two laminated layers, and is laminated and adhered as a shift amount within a range that a writing pickup of the drive device can follow.