JP2003272229A - Phase change type optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase change type optical recording medium having a refractive index and a signal amplitude practically sufficient, capable of repeating excellent recording and providing a sufficient reliability even when being stored under a high temperature high humidity environment. <P>SOLUTION: In the phase change type optical recording medium wherein at least a first dielectric layer, a recording layer, a second dielectric layer, an intermediate layer, and a reflecting heat dissipation layer are sequentially stacked on a transparent substrate, and the recording layer causes a reversible phase change between an amorphous phase and a crystalline phase through emission of a laser beam to record or erase information, the film thickness of the intermediate layer is selected to be 1 to 10 nm and the thermal conductivity is selected to be 0.03 to 0.3 W/cm-K, or the film thickness of the intermediate layer is selected to be 1 to 10 nm and a complex refractive index and a recording/reproducing wavelength (=n-ik, where n is a real part of the complex refractive index and k is an imaginary part of the complex refractive index) is selected to be 2.5 or over for the n and less than 0.3 for the k. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable phase-change optical recording medium capable of recording and reproducing information as with an information recording medium such as a compact disc.

[0002]

2. Description of the Related Art As one of optical recording media capable of recording, reproducing and erasing information by irradiating a laser beam, a transition between a crystalline-amorphous phase (amorphous phase) or a crystalline-crystalline phase is utilized. So-called phase change type optical recording media are well known. This recording medium is characterized in that it can be overwritten by a single beam, and the optical system on the drive side is simpler, and is applied as a recording medium for computer and audiovisual. As the recording material, GeTe, GeTeSe, GeTeS, Ge
SeS, GeSeSb, GeAsSe, InTe, Se
Te, SeAs, GeTe (Sn, Au, Pd), Ge
InSbTe, GeTeSb, GeGaSbTe, Ag
InSbTe and the like can be mentioned. In particular, Ag-In-S
Since b-Te has the characteristics of high sensitivity and a clear outline of the amorphous part, it is a phase-change type light that can achieve dramatic improvements in C / N, erase ratio, sensitivity, and recording / erasing repeatability characteristics compared to conventional ones. For the purpose of providing a recording medium, the composition thereof is disclosed in JP-A-8-22644.

[0003]

DISCLOSURE OF THE INVENTION The present invention has practically sufficient reflectance and signal amplitude, can perform good recording repeatedly, and exhibits sufficient reliability even when stored in a high temperature and high humidity environment. An object is to provide a phase change type optical recording medium.

[0004]

[Means for Solving the Problems] The above problems are solved in the following 1) to
It is solved by the invention of 3). 1) At least a first dielectric layer, a recording layer, and a transparent substrate,
A second dielectric layer, an intermediate layer, and a reflection / heat dissipation layer are sequentially laminated, and the recording layer undergoes reversible phase change between an amorphous phase and a crystalline phase by irradiation of laser light to record or erase information. A phase change type optical recording medium, wherein the intermediate layer has a film thickness of 1 to 10 nm and a thermal conductivity of 0.03 to 0.
A phase-change optical recording medium characterized by having a power of 3 W / cm · K. 2) At least the first dielectric layer, the recording layer, and the transparent substrate,
A second dielectric layer, an intermediate layer, and a reflection / heat dissipation layer are sequentially laminated, and the recording layer undergoes reversible phase change between an amorphous phase and a crystalline phase by irradiation of laser light to record or erase information. A phase change type optical recording medium, wherein the intermediate layer has a film thickness of 1 to 10 nm, a complex refractive index (= n-ik, n is a real part of the complex refractive index, and k is a complex refractive index at a recording / reproducing wavelength. The phase-change optical recording medium is characterized in that n of the imaginary part of the ratio is 2.5 or more and k is less than 0.3. 3) The intermediate layer is made of at least one of amorphous silicon, hydrogenated amorphous silicon, amorphous silicon carbide, and hydrogenated amorphous silicon carbide. Phase change type optical recording medium.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual diagram showing an example of the layer structure of the phase-change optical recording medium of the present invention, in which a first dielectric layer (heat-resistant protective layer) is formed on a transparent substrate 1 having guide grooves (not shown). ) 2, recording layer 3, second dielectric layer (heat resistant protective layer)
4, the intermediate layer 5, and the reflection / heat dissipation layer 6 are laminated in this order. Further, if necessary, an environment protection layer made of a UV curable resin may be provided on the reflection / heat dissipation layer.

As the material of the substrate, glass, ceramics or resin is usually used, but a resin substrate is preferable from the viewpoint of moldability. Specific examples of the resin include a polycarbonate resin, an acrylic resin, an epoxy resin, a polystyrene resin, a polyethylene resin, a polypropylene resin, a silicone resin, a fluororesin, an ABS resin, a urethane resin, and the like. Polycarbonate resin is preferred. The substrate may have a disc shape, a card shape, or a sheet shape.

As a material for the first and second dielectric layers, Si is used.
O, SiO_Two, ZnO, SnO_Two, Al_TwoO_Three, TiO
_Two, In_TwoO_Three, MgO, ZrO_TwoMetal oxides such as;
Si _ThreeN_FourNitrogen of AlN, TiN, BN, ZrN, etc.
Thing; ZnS, In_TwoS_Three, TaS_FourSulfide such as; Si
C, TaC, B_FourCarbonization of C, WC, TiC, ZrC, etc.
Thing, diamond-like carbon, or a mixture of
Can be mentioned. These materials may be used alone as a protective layer.
However, they may be mixed with each other. Also, if necessary
It is also possible to form a laminated film of them. However, first
The melting point of the second dielectric layer is higher than that of the recording layer 3.
is necessary. Such first and second dielectric layers are various
Vapor deposition methods such as vacuum evaporation, sputtering,
Plasma CVD method, photo CVD method, ion plating
Method, electron beam evaporation method, or the like.

The thickness of the first dielectric layer is 30 to 200n.
m, preferably 50 to 120 nm. When the thickness is less than 30 nm, the function as the heat resistant protective layer cannot be achieved, and conversely, when the thickness is more than 200 nm, the sensitivity is lowered. Further, the first dielectric layer can be multi-layered if necessary. The film thickness of the second dielectric layer is 10 to 35 nm, preferably 15 to 30 nm. If it becomes thinner than 10 nm, it will no longer function as a heat resistant protective layer, and conversely 35
If the thickness is thicker than nm, the repetitive recording performance deteriorates. Further, the second dielectric layer can be multi-layered if necessary.

As the reflection and heat dissipation layer, Al, Au, Ag,
A metal material such as Cu or an alloy thereof can be used. Among these, Ag simple substance, Ag alloy, and Al alloy are particularly preferable because they are excellent in cost and environment resistance, and alloy components include Au, Pt, Pd, Ru, Ti, and C.
u and Ta are excellent. Such a reflective heat dissipation layer can be formed by various vapor deposition methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method and electron beam evaporation method. The characteristics of the reflection / heat dissipation layer are high thermal conductivity, high melting point, and good adhesion to the intermediate layer. Especially, it is one of the important functions to efficiently dissipate heat, and the film thickness is 80-
The thickness is 200 nm, preferably 100 to 180 nm. If the film thickness is too thick, the heat dissipation efficiency will be too good and the sensitivity will deteriorate,
If it is too thin, the sensitivity will be good, but the repeated overwrite characteristics will be poor.

The intermediate layer needs to have a film thickness of 1 nm or more. If it is less than 1 nm, it does not function as a continuous thin film and local abnormalities occur in recording characteristics, which is not practical. If the thickness is preferably 2 nm or more, the reproducibility of repeated film formation and the in-plane uniformity during continuous mass production can be guaranteed. Therefore, it is particularly effective when a second dielectric layer containing sulfur and a silver reflection heat dissipation layer are used. On the other hand, when the thickness exceeds 10 nm, the light absorption in the intermediate layer becomes large, so that the reflectance and the sensitivity decrease.
When it is not more than m, repeated recording stability and reflectance can be improved. Furthermore, the thermal conductivity of the intermediate layer is 0.03.
By setting the ratio to W / cm · K or more, it is possible to prevent the quenching effect of the metal reflection / radiation layer having high thermal conductivity from being impaired. More preferably, 0.04 W / cm · K or more can obtain a practically sufficient signal amplitude.

By setting the complex index of refraction (= n-ik, n is the real part of the complex index, k is the imaginary part of the complex index) of the intermediate layer at the wavelength of the recording / reproducing light to be 2.5 or more. Since the refractive index of ZnS.SiO ₂ (molar ratio 80:20) most commonly used as the second dielectric layer is about 2 to 2.1, the optical effect of the second dielectric layer is not impaired. You can Further, by setting k to be less than 0.3, it is possible to prevent a decrease in sensitivity and reflectance due to light absorption of the intermediate layer. Amorphous silicon and amorphous silicon carbide are particularly suitable as materials satisfying these conditions, and if hydrogenated amorphous silicon or hydrogenated amorphous silicon carbide is used, k (complex refractive index imaginary Since the (part) can be made small, it is possible to obtain an intermediate layer which is transparent without absorption and does not impair the thermal characteristics.

[0012]

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

Example 1 A substrate is made of a polycarbonate resin, and first and second dielectric layers are made of Z resin.
nS.SiO ₂ (molar ratio 80:20), Ag recording layer
_1.5 In _7.0 Sb _67.0 Te _24.5 , the intermediate layer is any one of amorphous silicon, amorphous silicon carbide, hydrogenated amorphous silicon, hydrogenated amorphous silicon carbide, The reflective heat dissipation layer was made of Ag, and the thickness of each layer other than the intermediate layer was set to 90 nm for the first dielectric layer, 16 nm for the recording layer, 20 nm for the second dielectric layer, and 150 nm for the reflective heat dissipation layer.
The phase change type optical recording medium having the layer structure shown in
-Speed CD-RW standard (Orange Boot
The recording / reproducing signal characteristics were evaluated based on kVol2 Ver1.0). As a result, as shown in FIG. 2, the thermal conductivity (W / cm · K) of the intermediate layer was 0.20 for amorphous silicon,
Amorphous silicon carbide 0.03, hydrogenated amorphous silicon 0.30, hydrogenated amorphous silicon carbide 0.0
6 and the thermal conductivity of the intermediate layer is 0.03 to 0.3 W / c.
It was confirmed that good modulation can be obtained when m · K and the thickness of the intermediate layer is in the range of 1 to 10 nm.

Example 2 A phase change optical recording medium was prepared in the same manner as in Example 1 and evaluated in the same manner. As shown in FIG. 3, the complex refractive index of the intermediate layer at a recording / reproducing wavelength of 780 nm was measured. The imaginary part k is amorphous silicon 0.1, amorphous silicon carbide 0.3,
Hydrogenated amorphous silicon is 0.05 and hydrogenated amorphous silicon carbide is 0.2, and since the real part n of the complex refractive index is 2.5 or more, the real part n of the complex refractive index is Was 2.5 or more, the imaginary part k was less than 0.3, and good reflectance was obtained in the range of the thickness of the intermediate layer from 1 to 10 nm.

[0015]

According to the present invention, it is possible to provide a phase change type optical recording medium having sufficient reflectance and contrast, and having high durability against repeated use and storage reliability.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a layer structure of a phase-change optical recording medium of the present invention.

FIG. 2 is a diagram showing the relationship between the film thickness and thermal conductivity of an intermediate layer and modulation in the optical recording medium of Example 1.

FIG. 3 is a diagram showing the relationship between the film thickness of the intermediate layer and the imaginary part of the complex refractive index at the recording / reproducing wavelength and the reflectance in the optical recording medium of Example 2.

[Explanation of symbols]

1 substrate 2 First dielectric layer 3 recording layers 4 Second dielectric layer 5 Middle class 6 Reflective heat dissipation layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuyuki Yamada             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F-term (reference) 5D029 HA04 NA13 NA14

Claims (3)

[Claims] 1. At least a first dielectric layer on a transparent substrate,
A recording layer, a second dielectric layer, an intermediate layer, and a reflection / heat dissipation layer are sequentially laminated, and the recording layer undergoes a reversible phase change between an amorphous phase and a crystalline phase upon irradiation with laser light to record or erase information. Of the intermediate layer having a film thickness of 1 to 10 nm and a thermal conductivity of 0.0.
A phase-change type optical recording medium characterized in that it is 3 to 0.3 W / cm · K. 2. At least a first dielectric layer on a transparent substrate,
A recording layer, a second dielectric layer, an intermediate layer, and a reflection / heat dissipation layer are sequentially laminated, and the recording layer undergoes a reversible phase change between an amorphous phase and a crystalline phase upon irradiation with laser light to record or erase information. And a complex refractive index at the recording / reproducing wavelength (= n-ik, n is a real part of the complex refractive index, k Is the imaginary part of the complex index of refraction n is 2.5 or more and k is less than 0.3. 3. The intermediate layer is made of at least one of amorphous silicon, hydrogenated amorphous silicon, amorphous silicon carbide, and hydrogenated amorphous silicon carbide. 2. The phase change type optical recording medium according to 2.