JP2003006923A - Phase change type optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase change type optical recording medium having a high linear velocity and high recording density. SOLUTION: (1) The phase change type optical recording medium has at least two recording layers on a substrate, the light incident side recording layer (first recording layer) contains at least SbTe and a protective layer situated nearer the middle of the medium than the first recording layer (on the side closer to the second recording layer) as one of protective layers adjacent to both sides of the first recording layer has >=50 W/m.deg heat conductivity and >=30% light transmittance. (2) In the phase change type optical recording medium, the protective layer situated nearer the middle of the medium than the first recording layer comprises any one of BeO, AlNx-Y2 O3 , MoSi or SiC.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium for recording / reproducing information by light of a laser or the like, and is particularly used for a computer memory, a memory for image and audio files, an optical card and the like. And a phase change optical recording medium.

[0002]

2. Description of the Related Art As an optical medium capable of recording / reproducing by irradiation with a laser beam, there are a phase change medium utilizing a crystal-amorphous transition and a dye medium utilizing a reflectance difference due to perforation of a dye. In a conventional optical recording medium, it was easy to form two pit layers from the light incident side in a read-only medium. However, when two recordable and reproducible layers are provided, one layer must satisfy the contradictory physical properties that light can be transmitted and light can be absorbed for recording. To be transparent means that absorption is small at a normal film thickness, and if a thick heat dissipation layer is provided, light is not transmitted and heat dissipation becomes insufficient, and it is difficult to be amorphous. Therefore, it is difficult to record at high speed or high density.

Optical discs such as CD-Rs and CD-RWs record signals such as sounds, characters and images along a circumferential direction on a circular plastic substrate made of polycarbonate or the like, or on a recording layer provided thereon. Then, a metal such as aluminum, gold, or silver is vapor-deposited or sputtered on the surface to form a reflective layer, and laser light is incident from the substrate surface side to record / reproduce signals. Since the amount of information handled by computers has increased in recent years, DVD-RA
The signal recording capacity of optical discs such as M and DVD-RW is increasing, and the density of signal information is increasing. The recording capacity of a CD is about 650 MB, and that of a DVD is about 4.7 GB, but a higher recording density is required in the future.
Then, as a means for realizing such a high recording density medium, it has been proposed to shorten the laser wavelength used to the blue light region. However, as a conventionally known technique, Japanese Unexamined Patent Publication No. 8-287474 discloses means for forming a multilayer, but there is no disclosure regarding a specific medium configuration, and Japanese Unexamined Patent Publication No. 9-198709 discloses
The phase change recording layer has two layers, and the layer through which light first transmits is Sb.
Although an example in which Se and another layer are made of Ge ₂ Sb ₂ Te ₅ is disclosed, it has been found that when high-speed recording is actually performed, the recording sensitivity deteriorates and high-density recording is difficult.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the current state of the art, and an object thereof is to provide a phase change type optical recording medium having a high linear velocity and a high recording density.

[0005]

[Means for Solving the Problems] The above problems are solved in the following 1) to
This is solved by the invention 2) (hereinafter, referred to as the present inventions 1 and 2). 1) At least two recording layers are provided on a substrate, the recording layer on the light incident side (hereinafter referred to as the first recording layer) includes at least SbTe, and the protective layers adjacent to both sides of the first recording layer are provided. Among them, the protective layer on the central side (the side closer to the second recording layer) than the first recording layer has a thermal conductivity of 50 W / m. A phase-change type optical recording medium having a degree of deg or more and a light transmittance of 30% or more. 2) protective layer of the first recording layer center side than the (side close to the second recording layer) _{is, BeO, AlNx-Y 2 O} 3, MoS
The phase change type optical recording medium according to 1), which is made of either i or SiC.

The present invention will be described in detail below. FIG. 1 shows the layer structure of an optical recording medium according to an embodiment of the present invention. The material of the substrate is usually glass, ceramics or resin, and a resin substrate is preferable in terms of moldability and cost. Examples of the resin include polycarbonate, acrylic resin, epoxy resin, polystyrene, acrylonitrile-
Examples thereof include styrene copolymer resin, polyethylene, polypropylene, silicone resin, fluorine resin, ABS resin, urethane resin, and the like, and polycarbonate and acrylic resin, which are excellent in moldability, optical characteristics, and cost, are preferable. An uneven pattern is formed on one side of the substrate surface, and a heat resistant layer, a recording layer, etc. are formed on this side. The thickness of the substrate is not particularly limited.

Both sides of the recording layer (first recording layer) on the light incident side
Of the protective layers adjacent to the
2) the protective layer 2 corresponding to the protective layer on the side closer to the recording layer)
The conductivity is 50 W / m. deg or more and light transmittance of 30
Must be at least%. Thermal conductivity is 50 W / m. d
If it is less than eg, the heat dissipation will be poor and the recording medium will be small.
High density because it is difficult to form a mark (amorphous mark)
There is a problem in recording, and the light transmittance is less than 30%
And recording power is insufficient for the second recording layer
Becomes impossible. Also, the thermal conductivity is 200 mW
/ Deg or more, heat is radiated too much and is absorbed by the recording layer.
Since it will not fit and the recording sensitivity will deteriorate, this area is the upper limit
Is. The upper limit of the light transmittance is that the protective layer 2 does not expose the second recording layer to light.
It may be 100% because it has a role of transmitting the. This
As a material satisfying such physical properties, for example, Be
O, AlNx-Y_TwoO _Three, MoSi, SiC, etc.
To be

The protective layer 1, the protective layer 3, and the protective layer 4 have the functions of preventing deterioration and alteration of the recording layer, enhancing the adhesive strength of the recording layer, and enhancing the recording characteristics. , SiO, SiO ₂ , ZnO, SnO ₂ , A
metal oxides such as 1 ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO and ZrO ₂ , Si ₃ N ₄ , AlN, TiN, BN,
Examples thereof include nitrides such as ZrN, sulfides such as ZnS, In ₂ S ₃ , and TaS ₄ , carbides such as TaC, B ₄ C, WC, TiC, and ZrC, diamond-like carbon, or a mixture thereof. These materials may be used alone as the protective layer, or may be mixed with each other. Moreover, you may contain an impurity as needed. Since the protective layer also functions as a heat resistant layer, its melting point must be higher than that of the recording layer. Such a protective layer may be formed by various vapor deposition methods such as vacuum deposition method, sputtering method and plasma CVD method.
Method, photo CVD method, ion plating method, electron beam evaporation method, or the like. Among them, the sputtering method is excellent in mass productivity and film quality.

As the heat dissipation layer, Al, Au, Ag, C
A metal material such as u or Ta, or an alloy thereof can be used. Further, as the additive elements, Cr, T
i, Si, Cu, Ag, Pd, Ta, etc. are used.
Such a reflection / heat dissipation layer can be formed by the same means as in the case of the protective layer, and the sputtering method is also excellent in mass productivity and film quality. As the recording layer, GeSbTe, AgInSbTe, SbTe, In
A phase change material that reversibly changes between a crystalline phase such as Te and an amorphous phase is used.

FIG. 2 shows a layer structure of an optical recording medium according to another embodiment of the present invention, in which a protective layer 1 is formed on a substrate.
1 to the heat dissipation layer are provided in the reverse order of FIG. 1, and a thin substrate is provided on the protective layer 1 via an adhesive layer. Thin substrate has high N
Since a thickness of 0.3 mm or less is required for the A (aperture ratio) objective lens, it is preferable to use a sheet-like material, and a resin material similar to the material of the substrate is preferably used as the material. To be Examples of the method for forming a light-transmitting layer using the transparent sheet include a method of attaching a transparent sheet via an ultraviolet curable adhesive or a transparent double-sided pressure-sensitive adhesive sheet. A light-transmitting layer may be formed by applying a curable resin on the protective layer and curing the resin.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 A protective layer 1 (ZnS.SiO ₂ ) of 40 nm and a recording layer 1 (Ag ₅ In ₅ Sb ₆₅ Te ₂₅ ) were formed on a polycarbonate substrate having a track pitch of 0.40 μm and a thickness of 0.6 mm.
The 15n 15 nm, the protective layer _{2 (AlNx-Y 2 O 3} )
m, a film was formed by a single-wafer sputtering apparatus, an ultraviolet curable resin layer was then provided by spin coating to a thickness of 10 μm, and transfer with a stamper was performed before the resin layer was cured. Transmittance of 88% of the protective layer _{2 (AlNx-Y 2 O 3} ) ( Wavelength 40
5 nm) and the thermal conductivity is 170 W / m. It was deg.
Next, the protective layer 3 (ZnS.SiO ₂ ) is 40 nm, the recording layer 2 (Ag ₅ In ₅ Sb ₆₅ Te ₂₅ ) is 12 nm, the protective layer 4 (ZnS · SiO) is 12 nm, and the heat dissipation layer (Ag).
Was sequentially deposited with a single-wafer sputtering apparatus to a thickness of 100 nm, and an organic protective layer (radical UV resin) was further formed to prepare an optical recording medium having the same layer configuration as in FIG.

Comparative Example 1 An optical recording medium was prepared in the same manner as in Example 1 except that the protective layer 2 was not provided.

The optical recording media of Example 1 and Comparative Example 1 were evaluated under the conditions of 400 nm, NA = 0.65, 6.5 m / s,
As a result of evaluation at 0.17 μm / bit, the modulation (recording / reproducing signal amplitude) of the recording layer 1 of Example 1 at the minimum jitter power was 20% higher than that of Comparative Example 1 and the jitter was 2% lower.

Example 2 Polycarbonate with a track pitch of 0.34 μm and a thickness of 0.6 mm
A heat dissipation layer (Ag) of 100 nm is kept on the carbonate substrate.
Protective layer 4 (ZnS / SiO_Two) Is 10 nm, recording layer 2 (A
g_TwoIn_ThreeSb₇₀Te₂₅) 15 nm, protective layer 3
(ZnS / SiO _Two) 30nm, single-wafer sputter
Film is formed by the device, and then UV-hardened by spin coating.
A resin layer of 20 μm is provided, and before the resin layer cures
Transfer was performed with a tamper. Next, the protective layer 2 (Be
O) 5 nm, recording layer 1 (Ge_TwoSb_TwoTe₅) 10
nm, protective layer 1 (ZnS / SiO_Two) 40 nm, in order
Next, a film is formed with a single-wafer sputter device, and then double-sided.
Sheet adhesive layer 25 μm, thin with a thickness of 0.1 mm
Adhesion of substrates to create an optical recording medium with the same layer structure as in Figure 2.
did. The transmittance of the protective layer 2 (BeO) is 85% (wavelength 40%).
5 nm) and the thermal conductivity is 51 W / m. It was deg.

Comparative Example 2 An optical recording medium was prepared in the same manner as in Example 2 except that the protective layer 2 was not provided.

The optical recording media of Example 2 and Comparative Example 2 were evaluated under the conditions of 400 nm, NA = 0.85, 6.0 m / s.
As a result of evaluation at 0.13 μm / bit, the modulation (recording / reproducing signal amplitude) of the recording layer 1 of Example 2 at the minimum jitter power was 33% higher than that of Comparative Example 2 and the jitter was 4% lower.

Example 3 A protective layer 1 (ZnS.SiO ₂ ) of 40 nm and a recording layer 1 (In ₄ Sb ₇₂ Te ₂₄ ) of 12 were formed on a polycarbonate substrate having a track pitch of 0.41 μm and a thickness of 0.6 mm.
nm, the stamper protecting layer _{2 (AlNx-Y 2 O 3} ) 5nm, sequentially deposited by single wafer sputtering apparatus, then, before providing 15μm ultraviolet curing resin layer by spin coating, the resin layer is cured Was performed. Next, the protective layer 3 (ZnS.SiO ₂ ) is 30 nm, the recording layer 2 (In ₄ Sb ₇₂ Te ₂₄ ) is 12 nm, and the protective layer 4 is
(ZnS / SiO) 12 nm, heat dissipation layer (Ag) 10
Films were sequentially formed with a single-wafer sputtering apparatus to have a thickness of 0 nm, and an organic protective layer (radical UV resin) was further formed to prepare an optical recording medium having the same layer structure as in FIG.

Comparative Example 3 The protective layer 2 was not provided, and the thickness of the protective layer 3 was 40 nm.
An optical recording medium was prepared in the same manner as in Example 3 except that

The optical recording media of Example 3 and Comparative Example 3 were evaluated under the conditions of 400 nm, NA = 0.65, 6.5 m / s,
As a result of evaluation at 0.17 μm / bit, the modulation (recording / reproducing signal amplitude) of the recording layer 1 of Example 3 at the minimum jitter power was 25% higher than that of Comparative Example 3, and the jitter was 3% lower.

Example 4 Polycarbonate with track pitch 0.36μm and thickness 0.6mm
A heat dissipation layer (Ag) of 100 nm is kept on the carbonate substrate.
Protective layer 4 (ZnS / SiO_Two) Is 10 nm, recording layer 2 (A
g_TwoIn_ThreeSb₇₀Te₂₅) 15 nm, protective layer 3
(ZnS / SiO _Two) 20 nm, single-wafer sputter
Film is formed by the device, and then UV-hardened by spin coating.
A resin layer of 20 μm is provided, and before the resin layer cures
Transfer was performed with a tamper. Next, the protective layer 2 (MoS
i) 7 nm, recording layer 1 (Ag_TwoIn_ThreeSb₇₀Te
₂₅) Is 10 nm, and the protective layer 1 (ZnS / SiO 2_Two) 4
0 nm, film is sequentially formed by a single-wafer sputtering apparatus, and further
On top of the double-sided sheet adhesive layer 0.02mm, thickness
A 0.08 mm thin substrate is adhered and the same layer structure as in FIG.
An optical recording medium was created. Transmittance of protective layer 2 (MoSi)
Is 83% (wavelength 405 nm) and the thermal conductivity is 60 W / m.
It was deg.

Comparative Example 4 The point that the protective layer 2 is not provided and the thickness of the protective layer 3 is 10 nm.
An optical recording medium was prepared in the same manner as in Example 4, except that

The optical recording media of Example 4 and Comparative Example 4 were evaluated under the conditions of 400 nm, NA = 0.85, 6.0 m / s,
As a result of evaluation at 0.14 μm / bit, the modulation (recording / reproducing signal amplitude) of the recording layer 1 of Example 4 at the minimum jitter power was 35% higher than that of Comparative Example 4 and the jitter was 5% lower.

Example 5 A protective layer 1 (ZnS.SiO ₂ ) of 40 nm and a recording layer 1 (Ge ₂ Sb ₂ Te ₅ ) of 15 n were formed on a polycarbonate substrate having a track pitch of 0.44 μm and a thickness of 0.6 mm.
m, a protective layer 2 (SiC) of 5 nm was sequentially formed by a single-wafer sputtering apparatus, then an ultraviolet curing resin layer of 15 μm was provided by spin coating, and transfer was performed by a stamper before the resin layer was cured. . The protective layer 2 (SiC) has a transmittance of 84% (wavelength 405 nm) and a thermal conductivity of 130 W.
/ M. It was deg. Next, the protective layer 3 (ZnS.Si
O ₂ ) of 30 nm, recording layer 2 (Ag ₂ In ₂ Sb ₇₂ T
e ₂₄ ) is 12 nm, and the protective layer 4 (ZnS / SiO) is 1 nm.
2 nm and a heat dissipation layer (Ag) having a thickness of 100 nm were sequentially formed by a single-wafer sputtering apparatus, and an organic protective layer (radical UV resin) was further formed to prepare an optical recording medium having the same layer structure as in FIG.

Comparative Example 5 The protective layer 2 is not provided, and the thickness of the protective layer 3 is 40 nm.
An optical recording medium was prepared in the same manner as in Example 5, except that

The optical recording media of Example 5 and Comparative Example 5 were evaluated under the conditions of 400 nm, NA = 0.65, 6.5 m / s, and
As a result of evaluation at 0.17 μm / bit, the modulation (recording / reproducing signal amplitude) of the recording layer 1 of Example 5 at the minimum jitter power was 22% higher than that of Comparative Example 5, and the jitter was 2% lower.

[0027]

According to the first and second aspects of the present invention, it is possible to provide a phase change type optical recording medium in which the recording layer on the light incident side can record at a high linear velocity and a high density.

[Brief description of drawings]

FIG. 1 is a diagram showing a layer structure of an optical recording medium according to an embodiment of the invention.

FIG. 2 is a diagram showing a layer structure of an optical recording medium according to another embodiment of the present invention.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) G11B 7/24 G11B 7/24 534K 534M 534N 535 535C

Claims (2)

[Claims] 1. A substrate having at least two recording layers, a recording layer on a light incident side (hereinafter referred to as a first recording layer) including at least SbTe, and being adjacent to both sides of the first recording layer. Among the protective layers, the protective layer on the center side (the side closer to the second recording layer) than the first recording layer has a thermal conductivity of 50 W / m.s.
A phase-change type optical recording medium having a degree of deg or more and a light transmittance of 30% or more. 2. The protective layer on the center side (closer to the second recording layer) than the first recording layer is BeO, AlNx—Y.
The phase change optical recording medium according to claim 1, wherein the phase change optical recording medium comprises any one of ₂ O ₃ , MoSi, and SiC.