JP2003006930A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium in which damage to a light transmissive protective layer by heat generated in data recording is suppressed without causing new problem even when the wavelength of light of a light source is made shorter and reliability is enhanced to increase rewrite frequency. SOLUTION: The optical recording medium has a substrate 15, an optical recording laminate 16 formed on the substrate 15 and a light transmissive protective layer 17 formed on the laminate 16 and the laminate 16 includes at least a phase change type optical recording layer 16RL, a first dielectric layer 16Ia formed on the protective layer 17 side of the recording layer 16RL and a cooling layer 16CL formed on the protective layer 17 side of the dielectric layer 16Ia, comprising nitride, oxide or the like of B, Al, Ga, In, C, Si, Ge or Sn and having a higher heat conductivity than the dielectric layer 16Ia.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical recording medium, and more particularly to an optical recording medium having a phase change type optical recording layer.

[0002]

2. Description of the Related Art In recent years, with the development of a technology for digitally recording data, various kinds of data such as video data such as moving images and still images, and audio data to be handled have been increasing in capacity. As the information recording medium for recording the large-capacity various data, an optical recording medium for optically recording information, a magnetic recording medium, and the like are widely used. As the above-mentioned information recording medium, a read-only memory (ROM: read only memory) for recording an information signal in an uneven shape by embossed pits or grooves.
There are y) type optical recording media, writable optical recording media using a phase change type optical recording layer, and magneto-optical recording media utilizing the magneto-optical effect.

Optical disc devices such as CDs (compact discs) and DVDs (digital versatile discs) are widely used as optical disc devices which use the above-mentioned optical recording medium, magneto-optical recording medium or the like (hereinafter also referred to as optical disc) as a recording medium. It is used. The increase in capacity of the above optical disk device is realized by shortening the wavelength of the laser light used and increasing the numerical aperture (NA) of the objective lens. Further, as the numerical aperture of this objective lens is increased, the disc tilt tolerance in the optical disc device is reduced. Therefore, in order to keep coma within the permissible range, the thickness of the layer that transmits light above the optical recording layer Needs to be thinned.

For example, in a CD or the like, the laser light wavelength is 780 nm band and the objective lens numerical aperture is 0.5,
The thickness of the light transmissive disc substrate on the upper layer of the optical recording layer is 1.2 mm. In DVDs, the laser light wavelength is 630 to 680 nm band, and the objective lens numerical aperture is 0.6.
And the thickness of the optically transparent disc substrate on the upper layer of the optical recording layer is 0.6 mm.
The substrates are stuck together and used as a 1.2 mm thick substrate.

Further, as a next-generation optical disk device capable of further increasing the capacity, the laser light wavelength is shortened to the blue to blue-violet region (for example, 380 to 420 nm band), and the numerical aperture of the objective lens is 0. .8 or more (for example, 0.8
There has been proposed an optical disk device using an optical recording medium having a high numerical aperture up to 5) and correspondingly reducing the thickness of a protective layer for transmitting light in the upper layer of the optical recording layer to about 0.1 mm. . In the above-mentioned optical disc, the 0.1 mm light transmitting layer lacks rigidity, so that 1.
A disk substrate of about 1 mm is used.

A phase change type optical disk will be described as an example of an optical disk in which the thickness of the light transmitting layer (light transmitting protective layer) is reduced to about 0.1 mm. Figure 10
FIG. 7A is a schematic perspective view showing how the optical disc is irradiated with light. The optical disc DC has a substantially disc shape with a center hole CH opened in the center, and is rotationally driven in the drive direction DR. When recording or reproducing information, the optical recording layer in the optical disk DC is
For example, light LT such as laser light in a blue to blue-violet region is emitted from the objective lens OL having a numerical aperture of 0.8 or more.

FIG. 10 (b) is a schematic sectional view.
FIG. 10C is an enlarged sectional view of a main part of the schematic sectional view of FIG. A groove 15a for partitioning a track region is provided on one surface of a disk substrate 15 made of polycarbonate or the like having a thickness of about 1.1 mm, and an optical recording laminate 16 is formed on this surface. The optical recording laminated body 16 includes, for example, the first dielectric layer 16Ia,
Phase change type optical recording layer 16RL, second dielectric layer 16I
b and the reflection film 16RF are laminated in this order. The layer structure and the number of layers of the optical recording laminate 16 differ depending on the type and design of the recording material. Further, a light-transmitting protective layer 1 having a film thickness of 0.1 mm is formed on the optical recording laminate 16.
7 are formed. The protective layer 17 is made of, for example, an ultraviolet curable resin.

When recording or reproducing the above-mentioned optical disc, a light L such as a laser beam is passed through the objective lens OL.
The optical recording laminate 16 is irradiated with T from the protective layer 17 side. During reproduction of the optical disc, the return light reflected by the optical recording laminate 16 is received by the light receiving element, the signal processing circuit generates a predetermined signal, and the reproduction signal is extracted.

In the optical disc as described above, the optical recording layered body 16 also has an irregular shape corresponding to the groove 15a provided on one surface of the disc substrate 15, and the groove 1
The track area is divided by 5a. A region protruding from the disk substrate 15 to the protective layer 17 side is called a land, and a recessed region is called a groove. A land-groove recording method for recording information on both the land and the groove can be applied. is there. It is also possible to use only one of the land and the groove as the recording area.

The phase change type optical disk having the above-mentioned structure records data depending on whether the phase change type optical recording layer is in a crystalline state or an amorphous state.
As the contrast of recorded data, at the wavelength of the light source used, the reflectance (Ra) as an optical disk when the optical recording layer is in an amorphous state, and the reflectance (R) as an optical disk when the optical recording layer is in a crystalline state
The layer structure and the like described above are designed so that the ratio (c / Ra) of c) becomes large. The wavelength of the light source used above is
As described above, the wavelength has been shortened from the 780 nm band or the 630 to 680 nm band to the 380 to 420 nm band, and along with this, the first dielectric is adjusted so that the above ratio (Rc / Ra) becomes optimum. It is important to set the film thickness of the layer 16Ia to an appropriate value.

When the film thickness of the first dielectric layer 16Ia is simulated, the reflectance (Ra and Rc) of the optical disk changes periodically with respect to the film thickness of the first dielectric layer 16Ia. , Ratio of contrast of recorded data when film thickness is 35 nm (Rc / Ra)
Is the maximum. Therefore, for example, the film thickness of the first dielectric layer 16Ia is set to about 35 nm.

[0012]

However, in the phase-change type optical disk having the above-mentioned structure, the protective layer 17 may be destroyed due to the following reasons. The protection layer 17 is destroyed by shortening the wavelength of the laser light used and increasing the numerical aperture (N) of the objective lens as described above.
Due to A), the light spot diameter of the laser light becomes smaller,
The energy density of the light spot on the optical disk increases, and a region of a high temperature exceeding 1000 ° C. locally occurs in the phase change optical recording layer during data recording, and this heat is transmitted through the thin first dielectric layer. It is considered that this is due to diffusion into a protective layer made of an ultraviolet curable resin or the like having low heat resistance. When the protective layer is destroyed as described above, the reliability of the optical disc is lowered, and the number of rewritable times is reduced.

Since the reflectivities (Ra and Rc) of the optical disk periodically change, the film thickness is increased to about 135 nm which is the film thickness in the next cycle when the ratio (Rc / Ra) becomes maximum, and A method of avoiding the above problems by suppressing the diffusion of heat generated in the variable optical recording layer to the protective layer has been considered. However, in this case, the manufacturing cost increases with the thickening of the first dielectric layer, the deterioration of cross-write due to heat being easily accumulated in the phase change optical recording layer, and
A new problem arises that it is difficult to maintain the film thickness accuracy.

The present invention has been made in view of the above situation. Therefore, the object of the present invention is to protect from the heat generated at the time of recording data even if the wavelength of the light source is shortened without causing a new problem. An object of the present invention is to provide an optical recording medium capable of suppressing layer breakage, improving reliability, and increasing the number of rewritable times.

[0015]

In order to achieve the above object, an optical recording medium of the present invention comprises a substrate, an optical recording laminate formed on the substrate, and an upper layer of the optical recording laminate. And a first dielectric formed on the protective layer side of the phase-change optical recording layer, the optical-recording laminate having at least a phase-transmissive protective layer formed thereon. A body layer and a cooling layer formed on the protective layer side of the first dielectric layer and having higher thermal conductivity than the first dielectric layer are included.

In the above-mentioned optical recording medium of the present invention, preferably, the optical recording laminate comprises a second dielectric layer formed on the substrate side of the phase change type optical recording layer, and the second dielectric layer. And a reflective film formed on the substrate side of the body layer.
More preferably, the optical recording layered body further includes a reflective film protective layer formed between the reflective film and the second dielectric layer.

In the above optical recording medium of the present invention, preferably, the cooling layer is B, Al, Ga, In, C, Si,
It contains at least one material selected from the group consisting of respective nitrides or oxides of Ge or Sn or mixtures thereof.

In the above-mentioned optical recording medium of the present invention, the total thickness of the first dielectric layer and the cooling layer is preferably 30.
~ 80 nm.

In the above optical recording medium of the present invention, preferably, the phase change type optical recording layer is made of an alloy represented by the following formula (1).

[0020]

Ge _a Sb _x Te _y (1) where 1-a = x + y, 0.02 ≦ a ≦ 0.10,
2.20 ≦ x / y ≦ 5.00.

In the above optical recording medium of the present invention, preferably, the phase change type optical recording layer is made of an alloy represented by the following formula (2).

[0022]

Embedded image Ge _a In _b Sb _x Te _y (2) where 1- (a + b) = x + y, 0.02 ≦ a + b ≦
0.10, 2.20 ≦ x / y ≦ 5.00.

In the above-mentioned optical recording medium of the present invention, the first dielectric layer formed on the light-transmissive protective layer side of the phase change type optical recording layer is further closer to the protective layer side than the first dielectric layer. Since the cooling layer with high thermal conductivity is formed, the heat generated during recording is quickly diffused, which prevents the protective layer from being destroyed by the heat generated during data recording even if the wavelength of the light source is shortened. However, it is possible to increase the reliability and increase the number of rewritable times. At this time, even if the first dielectric layer and the cooling layer are combined, the total film thickness can be reduced to about 30 to 80 nm, so that the above-mentioned new problem such as deterioration of cross light does not occur.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

First Embodiment FIG. 1A is a schematic perspective view showing how the phase change type rewritable optical disk according to this embodiment is irradiated with light. The optical disc DC has a substantially disc shape with a center hole CH opened in the center, and is rotationally driven in the drive direction DR. When recording or playing back information,
The optical recording layer in the optical disc DC is irradiated with light LT such as laser light in a blue to blue-violet region by an objective lens OL having a numerical aperture of 0.8 or more, for example.

FIG. 1B is a schematic sectional view.
FIG. 1C is an enlarged sectional view of a main part of the schematic sectional view of FIG. A groove 15a for partitioning a track area is provided on one surface of a disk substrate 15 made of polycarbonate or the like having a thickness of about 1.1 mm, and on this surface,
An optical recording laminated body 16 is formed. Furthermore, a light-transmitting protective layer 17 having a film thickness of 0.1 mm is formed on the upper layer of the optical recording laminate 16. The protective layer 17 is made of, for example, an ultraviolet curable resin.

When recording or reproducing the above-mentioned optical disc, a light L such as a laser beam is passed through the objective lens OL.
The optical recording laminate 16 is irradiated with T from the protective layer 17 side. During reproduction of the optical disc, the return light reflected by the optical recording laminate 16 is received by the light receiving element, the signal processing circuit generates a predetermined signal, and the reproduction signal is extracted.

In the optical disc as described above, the optical recording layered body 16 also has an uneven shape corresponding to the groove 15a provided on one surface of the disc substrate 15, and the groove 1
The track area is divided by 5a. A region protruding from the disk substrate 15 to the protective layer 17 side is called a land, and a recessed region is called a groove. A land-groove recording method for recording information on both the land and the groove can be applied. is there. It is also possible to set only one of the land and the groove as the recording area.

In the optical recording laminate 16, for example, a cooling layer 16CL, a first dielectric layer 16Ia, a phase change type optical recording layer 16RL, a second dielectric layer 16Ib, and a reflective film 16RF are arranged in this order from the upper layer side. It is stacked. The layer structure and the number of layers of the optical recording laminate 16 differ depending on the type and design of the recording material.

The optical recording layer 16RL is, for example, GeSbT.
It consists of a phase change material such as e. For example, the alloy represented by the following formula (1) or (2) can be preferably used.

[0031]

Ge _a Sb _x Te _y (1) where 1-a = x + y, 0.02 ≦ a ≦ 0.10,
2.20 ≦ x / y ≦ 5.00.

[0032]

Embedded image Ge _a In _b Sb _x Te _y (2) where 1- (a + b) = x + y, 0.02 ≦ a + b ≦
0.10, 2.20 ≦ x / y ≦ 5.00.

The reflection film 16RF also functions as a heat sink and is made of, for example, an aluminum alloy or an Ag alloy. The dielectric layers (16Ia, 16Ib) are ZnS-
It is made of a dielectric material such as SiO ₂ or a laminated body thereof.

The cooling layer 16CL has a higher thermal conductivity than the first dielectric layer 16Ia, and is, for example, B, Al, Ga, In, C, Si, Ge or Sn.
Of at least one material selected from the group consisting of respective nitrides or oxides or mixtures thereof. The first dielectric layer 16Ia is ZnS-SiO ₂
In the case of a film, a silicon nitride (Si ₃ N ₄ ) film or the like can be preferably used as the cooling layer 16CL.

In the phase-change type optical disc having the above-mentioned layer structure, the optical recording layer 16R in the region where the recording mark is to be formed with light having a higher intensity during recording than during reproduction.
Irradiate L. At this time, the optical recording layer 16R that received light
L changes to an amorphous state and becomes a recording mark. On the other hand, at the time of reproduction, reproduction light is applied to the optical recording layer 16RL. At this time, since the reflectance of the optical disk is different between the case where the optical recording layer 16RL is in the crystalline state and the case where it is in the amorphous state, the recorded data is reproduced by detecting the reflectance of the reproduction light. be able to.

Conventionally, the light-transmitting protective layer 17 is destroyed by heat generated in the optical recording layer 16RL when the above-mentioned strong light for recording is irradiated, and the reliability of the optical disk is deteriorated, and the number of rewritable times is increased. However, in the optical disc according to the present embodiment, the protective layer further includes the first dielectric layer 16Ia formed on the light-transmissive protective layer 17 side of the phase-change optical recording layer 16RL. Since the cooling layer 16CL having higher thermal conductivity than that of the first dielectric layer 16Ia is formed on the 17 side, heat generated during recording is quickly diffused, which allows data to be generated even if the wavelength of the light source is shortened. It is possible to suppress destruction of the protective layer 17 due to heat generated during the recording, improve reliability, and increase the number of rewritable times. As a result, it is possible to realize an optical disk that is compatible with a shorter wavelength of laser light and a higher numerical aperture (NA) of an objective lens as the capacity of an optical disk increases.

The first and second dielectric layers (16Ia, 16Ia
Ib) is formed for the purpose of adjusting the phase or the thermal conductivity, and further for the reason of preventing diffusion. However, the layer between the optical recording layer 16RL and the protective layer 17 is the cooling layer 16CL and the first layer. The laminated body of the dielectric layers 16Ia is designed so that the phase or the thermal conductivity has a predetermined value. For example, the total thickness of the first dielectric layer 16Ia and the cooling layer 16CL is set to 30 to 80 nm. By providing the cooling layer 16CL, the protective layer can be prevented from being destroyed even if heat is sufficiently diffused, so that the total thickness of the first dielectric layer 16Ia and the cooling layer 16CL can be reduced. Thus, it is possible to avoid an increase in manufacturing cost, a deterioration in cross-write, a difficulty in maintaining the film thickness accuracy, and the like, which occur when the first dielectric layer 16Ia is thickened.

In addition, the first dielectric layer 16Ia and the cooling layer 16
As the CL composite film, its film thickness is selected so that the contrast of the recorded data is increased. FIG. 2 shows the reflectance (Ra) as an optical disk when the optical recording layer is in the amorphous state when the light source wavelength is in the 400 nm band and the optical disk when the optical recording layer is in the crystalline state in the optical disk having the above-mentioned configuration. Reflectance (R
First dielectric layer 1 in which c) is converted to a ZnS-SiO ₂ film
It is a diagram showing a more determined results of the simulation to the composite thickness t ₁ of 6Ia cooling layer 16CL. The reflectivities (Ra and Rc) of the optical disk periodically change with respect to the composite film thickness t ₁ , and when the film thickness is 35 nm, the ratio of contrast of recorded data (Rc / Ra) becomes maximum. Therefore, it is preferable to set the composite film thickness t ₁ to about 35 nm.

For example, the first dielectric layer 16Ia which is a ZnS-SiO ₂ film is 25 nm, and the cooling layer 16CL which is a Si ₃ N ₄ film is 25 nm. The result of setting in this way is that the total thickness of the first dielectric layer 16Ia and the cooling layer 16CL is 50n in addition to satisfying the preferable condition of the composite thickness.
m, and the above-mentioned first dielectric layer 16Ia and cooling layer 16C
The preferable condition regarding the total film thickness of L is satisfied.

A method for manufacturing the above-mentioned optical disc of this embodiment will be described. First, as shown in FIG. 3A, a disk master having a resist film 11 formed on a glass substrate 10 is prepared.

Next, as shown in FIG. 3B, the resist film 1 is formed in a pattern in which, for example, a region of the disk substrate, which becomes a groove, is exposed by a laser beam or an electron beam.
1 exposure is performed and development processing is performed to form a resist film 11a having a pattern of opening a region to be a groove of the disk substrate.

Next, as shown in FIG. 4C, the metal master 12 is formed on the resist film 11a on the glass substrate 10 by using, for example, a silver plating process or another film forming process.
To form. On the surface of the metal master 12, the unevenness of the pattern formed by the glass substrate 10 and the resist film 11a and the unevenness of the reverse pattern are transferred.

Next, as shown in FIG. 4D, a mother 13 is formed on the metal master 12. On the surface of the mother 13, irregularities having a pattern opposite to that of the irregularities on the surface of the metal master 12 are transferred. In the drawing, the metal master 12 is shown as a lower side and the drawing is reversed upside down with respect to FIG.

Next, as shown in FIG. 5E, a stamper 14 is formed on the mother 13. On the surface of the stamper 14, the unevenness of the pattern opposite to the unevenness of the surface of the mother 13 is transferred. In the drawing, the mother 13 is set downward, and FIG.
It is drawn upside down with respect to (d).

Next, as shown in FIG. 5F, for example, an injection molding method, a compression molding method, or 2P (Photo P) is used.
The disk substrate 15 which is a resin substrate made of polycarbonate or the like is formed on the concave-convex pattern of the stamper 14 by an olymization method or the like. On the disk substrate 15, a groove 15c, which has an uneven pattern opposite to that of the surface of the stamper 14, is transferred. Here, the groove 15c, which is an uneven pattern having a pattern reverse to that of the surface of the stamper 14, is transferred. In the drawing, the stamper 14 is set downward, and FIG.
It is drawn upside down with respect to (e).

Next, as shown in FIG. 6G, on the surface of the disk substrate 15, for example, by a sputtering method or the like, for example, the reflection film 16RF, the dielectric layer 16Ib, the optical recording layer 16RL, the dielectric layer 16Ia, and cooling. A laminated body of the layer 16CL is formed in this order to form the optical recording laminated body 16.

Next, as shown in FIG. 6 (h), an ultraviolet curable resin, for example, is formed on the upper layer of the optical recording laminate 16,
The light-transmitting protective layer 17 is formed. As described above, the optical disc having the structure shown in FIG. 1 can be manufactured.

According to the optical disc manufacturing method of the present embodiment, the protective layer 17 is further provided on the first dielectric layer 16Ia formed on the light-transmissive protective layer 17 side of the phase-change optical recording layer 16RL. On the side, the cooling layer 16CL having a higher thermal conductivity than the first dielectric layer 16Ia is formed, and the heat generated during recording is quickly diffused.
Even if the wavelength of the light source is shortened, it is possible to manufacture an optical disc that can suppress the destruction of the protective layer 17 due to heat generated during data recording, improve reliability, and increase the number of rewritable times.

Second Embodiment FIG. 7 is an enlarged sectional view of a main part of a phase change type rewritable optical disk according to this embodiment. The phase change type optical disk according to the present embodiment has substantially the same configuration as the optical disk according to the first embodiment, but the second dielectric layer 1
Between the 6Ib and the reflective film 16RF, the reflective film protective layer 16PT
Are formed differently. For example, the reflective film 16R
F is made of Ag or the like, and the second dielectric layer 16Ib is ZnS.
If the second dielectric layer 16Ib is made of a SiO ₂ film or the like,
The reflection film 16RF may react with each other due to diffusion, but at this boundary portion, as the reflection film protection layer 16PT,
For example, the reflection film can be protected by forming a film that suppresses diffusion, such as a Si ₃ N ₄ film. The configuration other than the above can be the same as that of the first embodiment.

The optical disk according to the present embodiment described above, like the first embodiment, has the first dielectric layer 16 formed on the light-transmissive protective layer 17 side of the phase change type optical recording layer 16RL.
Since the cooling layer 16CL having a higher thermal conductivity than that of the first dielectric layer 16Ia is formed further on the protection layer 17 side of Ia, the heat generated during recording is quickly diffused, thereby shortening the light source. Even if the wavelength is changed, it is possible to suppress the destruction of the protective layer 17 due to the heat generated at the time of recording data, improve the reliability, and increase the number of rewritable times.

(Example) In this example, a phase change type optical disk having an optical recording laminate having the layer structure shown in FIG. 7 was prepared. That is, a film thickness 10 of Ag alloy is formed on a substrate 15 made of polycarbonate or the like having a thickness of about 1.1 mm and having a groove for separating a land and a groove formed therein.
0 nm reflective film 16RF, film thickness of Si ₃ N ₄ film 1
0 nm reflection film protective layer 16PT, ZnS (80 mol%)
A mixed-dielectric layer 16Ib made of --SiO ₂ (20 mol%) and having a thickness of 5 nm, and a phase change type optical recording layer 16R made of Ge _0.040 Sb _0.714 Te _0.246 alloy and having a thickness of 10 nm.
L, a mixed dielectric layer 16Ia made of ZnS (80 mol%)-SiO ₂ (20 mol%) and having a film thickness of 25 nm, and
Cooling layer 16CL made of Si ₃ N ₄ and having a thickness of 25 nm
Were sequentially laminated by a sputtering method to form a phase change type optical recording laminate 16. Next, on the upper layer of the optical recording laminate 16, a light-transmitting protective layer 17 made of an ultraviolet curable resin and having a film thickness of about 0.1 mm was formed by spin coating.

Signals were recorded on the phase-change type optical disk produced as described above at a bit length of 0.13 μm and a linear velocity of 5.42 m / sec, and the rewriting characteristics (jitter rewriting frequency dependence) were measured for land and groove. I examined each of the. The results are shown in Fig. 8.

(Comparative Example) In this example, an optical recording laminate having a layer structure shown in FIG. 10 and further having a reflective film protective layer formed between the second dielectric layer 16Ib and the reflective film 16RF was prepared. A phase change type optical disc having the above was prepared. That is, a film made of a reflection film 16RF made of Ag alloy and having a film thickness of 100 nm, and a film made of Si ₃ N _{4 made} of polycarbonate or the like having a thickness of about 1.1 mm and formed with a groove for separating a land and a groove. A reflection film protective layer having a thickness of 10 nm and a mixed dielectric layer 16Ib, G made of ZnS (80 mol%)-SiO ₂ (20 mol%) and having a thickness of 5 nm.
e _0.040 Sb _0.714 Te _0.246 Film thickness of 10n
m phase change type optical recording layer 16RL and ZnS
A mixed dielectric layer 16Ia made of (80 mol%)-SiO ₂ (20 mol%) and having a film thickness of 40 nm was sequentially laminated by a sputtering method to form a phase change type optical recording laminate 16. Next, the film thickness of the ultraviolet curable resin is about 0.1 by the spin coating method on the upper layer of the optical recording laminate 16.
A mm transparent protective layer 17 was formed.

Signals were recorded on the phase-change type optical disk produced as described above at a bit length of 0.13 μm and a linear velocity of 5.42 m / sec, and the rewriting characteristics (dependence of the number of rewritings of jitter) were recorded on land and groove. I examined each of the. The results are shown in Fig. 9.

From FIG. 9, the optical disc of the comparative example starts to increase the jitter on the order of several hundred rewrites, but from FIG. 8, the optical disc of the example of the present embodiment starts to increase the jitter. It was on the order of 10,000 times, and it was confirmed that the number of rewritable digits by two digits can be increased as compared with the comparative example.

The present invention is not limited to the above embodiment. For example, the layer constitution of the optical recording laminate and the material of each layer are not limited to those exemplified above, and the layer constitution and the material of each layer capable of realizing the above characteristics can be appropriately used. In addition, various modifications can be made without changing the gist of the present invention.

[0057]

According to the optical recording medium of the present invention, the first layer formed on the light-transmissive protective layer side of the phase change type optical recording layer.
Since the cooling layer having higher thermal conductivity than the first dielectric layer is formed further on the protective layer side of the dielectric layer, the heat generated at the time of recording is quickly diffused, which allows the light source to emit light with a short wavelength. Even if this is done, it is possible to suppress the destruction of the protective layer due to the heat generated at the time of recording data, improve the reliability, and increase the number of rewritable times.

[Brief description of drawings]

FIG. 1A is a schematic perspective view showing a state of light irradiation of an optical disc according to a first embodiment, and FIG.
Is a schematic cross-sectional view, and FIG. 1C is a cross-sectional view in which a main part of the schematic cross-sectional view of FIG. 1B is enlarged.

FIG. 2 is a reflectance (Ra) as an optical disc when the optical recording layer of the first embodiment is in an amorphous state and a reflectance (Rc) as an optical disc when the optical recording layer is in a crystalline state. 3] is a diagram showing a result obtained by simulation.

FIG. 3 is a cross-sectional view showing the manufacturing process of the optical disc manufacturing method according to the first embodiment, wherein (a) shows a process for forming a disc master, and (b) shows an exposing and developing process. Show.

FIG. 4 shows a step following that of FIG. 3, in which (c) shows a step of forming a metal master and (d) shows a step of forming a mother.

5 shows a step following that of FIG. 4, wherein (e) shows a step of forming a stamper and (f) shows a step of forming a disk substrate.

6 shows a step following that of FIG. 5, in which (g) shows a step up to forming an optical recording laminate, and (h) shows a step up to forming a protective layer.

FIG. 7 is an enlarged cross-sectional view of an essential part of the optical disc according to the second embodiment.

FIG. 8 is a diagram showing rewriting characteristics of the optical disc in the example.

FIG. 9 is a diagram showing a rewriting characteristic of an optical disc according to a comparative example.

FIG. 10 (a) is a schematic perspective view showing a state of light irradiation of an optical disc according to a conventional example, and FIG.
FIG. 10C is a schematic cross-sectional view, and FIG. 10C is an enlarged cross-sectional view of the main part of the schematic cross-sectional view of FIG. 10B.

[Explanation of symbols]

Reference numeral 10 ... Substrate, 11, 11a ... Resist film, 12 ... Metal master, 13 ... Mother, 14 ... Stamper, 15 ... Disk substrate, 15a ... Groove, 16 ... Optical recording laminate, 16RL
… Optical recording layer, 16CL… Cooling layer, 16RF… Reflective layer,
16Ia, 16Ib ... Dielectric layer, 16PT ... Reflective film protective layer, 17 ... Protective layer, CH ... Center hole, DC ... Optical disk, DR ... Drive direction, LT ... Light, OL ... Objective lens.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B41M 5/26 B41M 5/26 X (72) Inventor Katsuhiro Seo 6-735 Kitashinagawa, Shinagawa-ku, Tokyo No. Sony Corporation (72) Inventor Yuji Kuroda 6-35 Kita-Shinagawa, Shinagawa-ku, Tokyo F-Term (reference) within Sony Corporation 2H111 EA23 FA01 FA14 FA21 FA23 5D029 HA05 HA06 HA07 JA01 JB18 LA12 LB07 LC17 MA27

Claims (7)

[Claims] 1. A substrate, an optical recording laminate formed on the substrate, and a light-transmitting protective layer formed on the upper layer of the optical recording laminate, wherein the optical recording laminate comprises: At least a phase-change optical recording layer, a first dielectric layer formed on the protective layer side of the phase-change optical recording layer, and a protective layer side of the first dielectric layer, 1. An optical recording medium including a cooling layer having a thermal conductivity higher than that of the first dielectric layer. 2. The optical recording laminate comprises a second dielectric layer formed on the substrate side of the phase change optical recording layer, and a reflective film formed on the substrate side of the second dielectric layer. The optical recording medium according to claim 1, further comprising: 3. The optical recording medium according to claim 2, wherein the optical recording layered body further includes a reflective film protective layer formed between the reflective film and the second dielectric layer. 4. The cooling layer comprises B, Al, Ga, In,
The optical recording medium according to claim 1, comprising at least one material selected from the group consisting of nitrides or oxides of C, Si, Ge, or Sn, or a mixture thereof. 5. The optical recording medium according to claim 1, wherein the total thickness of the first dielectric layer and the cooling layer is 30 to 80 nm. 6. The phase change type optical recording layer has the following formula (1):
The optical recording medium according to claim 1, which is made of the alloy shown in. Embedded image Ge _a Sb _x Te _y (1) where 1-a = x + y, 0.02 ≦ a ≦ 0.10,
2.20 ≦ x / y ≦ 5.00. 7. The phase change type optical recording layer has the following formula (2):
The optical recording medium according to claim 1, which is made of the alloy shown in. Embedded image Ge _a In _b Sb _x Te _y (2) where 1- (a + b) = x + y, 0.02 ≦ a + b ≦
0.10, 2.20 ≦ x / y ≦ 5.00.