JPH0869636A - Optical information recording medium - Google Patents

Abstract

PURPOSE: To obtain a phase change type optical information recording medium having a high C-N ratio and a high erasure ratio and capable of repeating recording and erasure many times by using specified elements as the constituents of a phase change type recording layer and forming a thin oxide film contg. a prescribed at.% or more of O as the substrate side layer of a protective layer consisting of two layers. CONSTITUTION: When a 1st protective layer 2 consisting of a substrate side layer 21 and a recording layer side layer 22, a phase change type recording layer 3, a 2nd protective layer 4 and a reflecting and heat radiating layer 5 or the like are laminated on a substrate 1 to obtain a phase change type optical information recording medium, Ag, In, Sb and Te are used as the principal constituent elements of the recording layer 3 and a thin oxide film contg. >=30at.% 0 is formed as the substrate side layer 21. The objective phase change type optical information recording medium having a high C-N ratio and a high erasure ratio and capable of repeating recording and erasure many times is obtd. The layer 21 is, e.g. made of (Zrx Ce1-x )y O1-y (where 0<=x<=1 and 0.25<=y<=0.4).

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,
In particular, the present invention relates to a phase-change type optical information recording medium which is applied to optical memory-related equipment, in which a recording layer material undergoes a phase change upon irradiation with a light beam to record and reproduce information, and can be rewritten.

[0002]

2. Description of the Related Art As one of optical memory media capable of recording, reproducing and erasing information by irradiation of electromagnetic waves, especially laser beams, so-called phase change utilizing a transition between a crystalline-amorphous phase or a crystalline-crystalline phase. Shaped optical information recording media are well known. This phase change type optical information recording medium,
In particular, magneto-optical memory is capable of overwriting with a single beam, which is difficult, and is simpler than the optical system on the drive side. Therefore, research and development have been actively conducted recently.

As a typical example thereof, USP35304
41, Ge-Te, Ge-Te.
-Sn, Ge-Te-S, Ge-Se-S, Ge-Se
-Sb, Ge-As-Se, In-Te, Se-Te,
Examples include so-called chalcogen-based alloy materials such as Se-As. For the purpose of improving stability and high-speed crystallization,
Proposal of a material in which Au (Japanese Unexamined Patent Publication No. 61-219692), Sn and Au (Japanese Unexamined Patent Publication No. 61-270190), Pd (Japanese Unexamined Patent Publication No. 62-19490), etc. are added to a Ge-Te system. , A material in which the composition ratio of Ge-Te-Se-Sb and Ge-Te-Sb is specified for the purpose of improving the recording / erasing repetition performance (Japanese Patent Laid-Open No. 62-73438).
Have been made.

However, none of them can satisfy all of the characteristics required for the phase change type rewritable optical memory medium. In particular, prevention of a reduction in the erase ratio due to the unerased portion at the time of overwriting and improvement of the number of repeated recordings are the most important issues to be solved.

From the above, Japanese Patent Laid-Open No. 63-2512
Japanese Patent Publication No. 90 proposes an optical information recording medium provided with a recording layer consisting of a multi-component compound single phase whose crystal state is substantially ternary or more. Here, the term "substantially ternary or higher multicomponent compound monolayer" means that the recording layer contains 90 atom% or more of a compound having a stoichiometric composition of ternary or higher (for example, In ₃ SbTe ₂ ). It is said that the recording and erasing characteristics can be improved by using such a recording layer.

However, these optical information recording media have drawbacks such as a low erasing ratio. Under these circumstances, it has been desired to develop an optical information recording medium having a high erasing ratio and excellent repetitive characteristics. As a measure for this, development of a protective layer material suitable for the recording layer material is promoted,
Materials such as ZnS.SiO ₂ (Japanese Patent Laid-Open No. 4-71785), SiN, AlN and the like are used. However, the fact is that the combination of these materials does not satisfy all the characteristics required for the optical information recording medium.

[0007]

The object of the present invention has been made in view of the above circumstances, and is a phase change in which the C / N and the erasing ratio are high and a large number of recording-erasing can be repeated. (EN) Provided is an optical information recording medium.

[0008]

The present inventor has studied and studied optical information recording media from various angles in order to achieve the above-mentioned objects. However, by combining recording layer materials and protective layer materials, It was found that excellent results were obtained with high C / N, high erasing ratio and excellent repeatability. The present invention has been made based on this.

That is, according to a first aspect of the present invention, at least a first protective layer, a phase-change recording layer (hereinafter sometimes referred to as "recording layer"), a second protective layer, and a reflection heat dissipation layer are sequentially provided on a plastic substrate. In the optical information recording medium, the main constituent elements of the recording layer are Ag, In, Sb and Te, and the first protective layer is composed of two layers, of which the layer on the substrate side is 30 atom% or more. It is characterized by being an oxide thin film containing O. Here, as a specific oxide thin film, (Zr _x Ce _1-x ) _y O _1-y (0 ≦ x ≦ 1, 0.25 ≦ y ≦
0.4) or Ta _x O _1-x (0.22 ≦ x ≦ 0.35) are suitable. On the other hand, a material represented by (Z _n S) _x (SiO ₂ ) _1-x (0.7 ≦ x ≦ 0.85) is suitable for the recording layer side of the two first protective layers. ing.

A second aspect of the present invention is an optical information recording medium in which at least a first protective layer, a recording layer, a second protective layer and a reflection / heat dissipation layer are sequentially provided on a plastic substrate, and the main constituent elements of the recording layer are Ag, In, Sb, and Te, and the second protective layer is a compound containing at least Si and N among Si, B, O, and N, and contains 30 atomic% or more of N. To do.

A third aspect of the present invention is an optical information recording medium in which at least a first protective layer, the recording layer, a second protective layer and a reflection / heat dissipation layer are sequentially provided on a plastic substrate, and the main constituent elements of the recording layer. Is Ag, In, Sb and Te, and the second protective layer is composed of two layers, of which the layer on the reflection and heat dissipation layer side is a nitride thin film containing 30 atom% or more of N. It is what Here, as a specific nitride thin film, a compound containing at least Si and N among Si, B, O, and N and containing 30 atom% or more of N, or B _x N _1-x (0. 4 ≦ x ≦
0.6) is suitable. The layer on the recording layer side of the second protective layer composed of two layers is (ZnS) _x (SiO ₂ )
_1-x (0.7 ≦ x ≦ 0.85) is suitable.

The present invention will be described in more detail below with reference to the accompanying drawings. 1A and 1B are schematic cross-sectional views of two typical examples of the optical information recording medium of the present invention. In these drawings, 1 is a plastic substrate, 2 is a first protective layer (21 is a layer on the substrate 1 side, 22 is a layer on the recording layer 3 side), 3
Is a recording layer, 4 is a second protective layer (41 is a layer on the recording layer 3 side, 4
Reference numeral 2 is a layer on the side of the reflective heat dissipation layer 5) and 5 is a reflective heat dissipation layer.

As the substrate 1 in the optical information recording medium of the present invention, a plastic substrate obtained by injection molding is used because glass is easily broken and expensive, and pregrooves are not easily formed. Specific examples of the material of the plastic substrate include polycarbonate (PC), polymethylmethacrylate (PMMA), and amorphous olefin (APO). Among them, polycarbonate (PC) has heat resistance and good transferability during injection molding. ) Is the most practical. These substrates are disk-shaped, and a thickness of about 0.6 to 1.2 mm is suitable.

Recording layer 3 in the optical information recording medium of the present invention
Is at least Ag, In, Sb and T as constituent elements.
It includes e. Other elements may be added for the purpose of further improving the disc characteristics. For example, transition metal elements such as IVa and Va (Ti, V, Cr,
(Zn, Nb, Mo, etc.) makes it easy to control the crystallization rate, and it is possible to improve structural stability and repeatability. The recording layer is often amorphous at the time of film formation, but is initialized by heat treatment after forming the medium.

The stable state (unrecorded portion) of these recording layers is
From the results of electron microscope observation, electron diffraction, and X-ray diffraction, the stoichiometric composition of the crystal phase or AgSb close to it
It is known that an amorphous phase composed of Te ₂ and at least In and Sb exists in a mixed phase state. The mixed phase state is AgSbTe or a stoichiometric composition.
Can take a state of amorphous phase comprising at least In and Sb are dispersed state or in an amorphous phase comprising at least In and Sb AgSbTe ₂ crystal phase is a state or their dispersed and mixed in ₂ crystalline phase.

The amorphous phase is generally said to have a highly isotropic structure. On the other hand, since AgSbTe ₂ also has a cubic crystal structure, which is an isotropic crystal structure, for example, when it is rapidly cooled from a high temperature by a laser beam to become an amorphous phase (transition from recording to metastable state), a uniform phase at high speed A change occurs, resulting in an amorphous phase with little physical or chemical variation. The fine structure of this amorphous phase is difficult to analyze and the details are unknown. For example, the stoichiometric composition of the amorphous phase or AgSbTe close to it
It is considered that a combination of ₂ and an amorphous phase composed of at least In and Sb, or a completely different single amorphous phase is formed. On the contrary, in the transition from the highly uniform amorphous phase to the isotropic crystal structure (transition from erasure to stable state), crystallization occurs uniformly, so that the erasure ratio is very high. Become. In the mixed state, the melting point will drop due to the size effect.
A phase transition can occur at relatively low temperatures. That is,
As a recording medium, recording sensitivity is improved.

Such a mixed phase state is caused by AgInTe ₂ and S.
It can be prepared by using b and b as raw materials. The recording film during film formation reflects the chemical structure of the raw materials and is Ag
It is considered to be an amorphous phase of InTe ₂ and Sb. This is because AgInTe ₂ and Sb are formed by heat treatment at a temperature near the crystallization transition point (190 to 220 ° C.).
It can be confirmed that the crystal phase of Initializing such a recording film with a laser beam having an appropriate power, heat, or the like creates a uniform amorphous mixed phase of AgSbTe ₂ and at least In and Sb, which has a fine stoichiometric composition or is close to the stoichiometric composition. be able to. That is, in a system containing at least Ag, In, Sb, and Te, an appropriate structure can be obtained by changing the structure by causing a substitution reaction as an initialization process for the recording film during film formation. This process consists of heating the recording film during film formation, bringing it into a molten or near-active state, and then cooling it at an appropriate cooling rate. If the cooling rate is too fast, the recording layer will have an amorphous structure, while if it is too slow, it will not have a preferable fine mixed phase structure, and the In and Sb phases will also crystallize.

[0018] The composition of the recording layer, when the _{(Ag α Sb α Te 1-2α)} x (In 1-y Sb y) 1-x, 0.1 <α <0.3 0.3 ≦ x The range of ≦ 0.5 0.7 ≦ y ≦ 0.9 is preferable. The recording layer in the present invention 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. Besides the vapor phase growth method, a wet process such as a sol-gel method can be regularly used. The thickness of the recording layer is 10 to 1000 nm,
It is preferably 20 to 300 nm. When the thickness is less than 10 nm, the light absorption ability is remarkably lowered and the recording layer does not function. If it is thicker than 1000 nm, a uniform phase change at high speed is unlikely to occur.

In the present invention, the first protective layer 2 consisting of two layers is first provided on the plastic substrate. Recording layer 3 AgI
Since the nSbTe-based material is likely to be corroded by oxidation or the like depending on temperature and humidity, it is necessary to cover both surfaces with a protective layer such as a dielectric film. Therefore, the first protective layer 2 must be a material that prevents the entry of water and oxygen from the substrate 1, has a high corrosion resistance itself, and has a low reactivity with the recording layer 3. As a specific material for the first protective layer 2,
SiO, SiO ₂ , ZnO / SnO ₂ , Al ₂ O ₃ , TiO
₂ , metal oxides such as In ₂ O ₃ , MgO and ZrO ₂ , Si
Metal nitrides such as ₃ N ₄ , AlN, TiN, BN and ZrN, metal sulfides such as ZnS, In ₂ S ₃ and TaS ₄ , S
Carbides such as iC, TaC, B ₄ C, WC, TiC and ZrC, diamond-like carbon and mixtures thereof are generally known.

On the other hand, however, when repetitive overwriting is performed, the recording layer 3 is repeatedly crystallized and amorphized in a short time, so that thermal damage is accumulated,
Partial peeling easily occurs at the interface between the first protective layer 2 and the substrate 1. Therefore, it is important to select a material for the first protective layer 2 that has a strong adhesion to the plastic substrate 1 in order to improve the repetitive overwrite characteristics. However, at present, there is no material satisfying all the above conditions.

The first protective layer 2 of the present invention comprises two layers,
A material having a large adhesion to the plastic substrate 1 is used for the layer 21 on the substrate side. An oxide thin film generally has a large adhesion to a plastic substrate, particularly a polycarbonate substrate. This tendency is particularly suitable for the layer 21 on the substrate side, which is an oxide thin film containing O of 30 atom% or more. Specific materials are as shown in the following formulas (1) and (2). (Zr _x Ce _1-x ) _y O _1-y (0 ≦ x ≦ 1, 0.25 ≦ y ≦ 0.4) Formula (1) Ta _x O _1-x (0.22 ≦ x ≦ 0 ..35) ... Formula (2)

On the other hand, of the first protective layer, the layer 2 on the recording layer side
2 is SiO, SiO ₂ , ZnO.SnO ₂ , Al
₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, ZrO ₂ and other metal oxides, Si ₃ N ₄ , AlN, TiN, BN, ZrN and other metal nitrides, ZnS, In ₂ S ₃ , TaS _4, etc. Metal sulfides, SiC, TaC, B ₄ C, WC, TiC, Zr
Carbides such as C, diamond-like carbon, and mixtures thereof can be mentioned. Among them, (ZnS) _x (Si
O ₂ ) _1-x (0.7 ≦ x ≦ 0.85) is preferable.

The film thickness of the first protective layer 2 is 10 to 100 nm, preferably 10 to 30 nm for the substrate-side layer 21, and 50 to 200 nm, preferably 100 to 200 for the recording layer-side layer 22.
It is 150 nm.

In the present invention, the second protective layer 4 is provided on the recording layer 3. The second protective layer 4 is also the same as the first protective layer 2 in the recording layer 3
Since it needs a function of protecting the recording layer, it must be a material that prevents intrusion of water and oxygen, has high corrosion resistance of itself, and has low reactivity with the recording layer 3. It is preferable to use a material having a high thermal conductivity in order to quickly release the heat of the recording layer 3 whose temperature has been raised by the laser beam to the reflection / heat dissipation layer (rapid cooling).

As the specific material, those listed for the first protective layer 2 are generally used. However, if overwriting is repeatedly performed in a short time, thermal peeling causes partial peeling at the interface between the second recording layer 4 and the reflection / heat dissipation layer 5 formed thereon. Therefore, in order to improve the repetitive overwrite characteristics, it is important to select a material having a large adhesion to the metal film such as the Al alloy which is the reflection / heat dissipation layer 5. The nitride thin film has a strong adhesion to the Al alloy that is the reflection / heat dissipation layer 5, and as the material of the second protective layer that satisfies the above-mentioned conditions, a nitride containing at least Si and N among Si, B, O, and N. A thin film containing N of 30 atom% or more is used.

As another method for satisfying the conditions for the second protective layer 4, the second protective layer 4 has a two-layer structure, and the layer 42 on the reflection and heat dissipation layer side of the second protective layer 4 is a nitride containing 30 atom% or more of N. It may be a thin film. In that case, as a specific material, at least Si among Si, B, O, and N described above is used.
Nitride thin films containing N and N containing 30 atom% or more are mentioned. In addition, B _x N _1-x (0.4 ≦ x ≦
0.6) is also acceptable. On the other hand, when the second protective layer 4 has a two-layer structure, the recording layer side layer 41 is made of SiO, SiO ₂ ,
_{ZnO · SnO 2, Al 2 O} 3, TiO 2, In 2 O 3, Mg
O, metal oxides such as ZrO ₂ , Si ₃ N ₄ , AlN, T
Metal nitride such as iN, BN, ZrN, ZnS, In ₂
Metal sulfides such as S ₃ and TaS ₄ , SiC, TaC, B ₄
Examples thereof include carbides such as C, WC, TiC, and ZrC, diamond-like carbon, and mixtures thereof. Among them, (ZnS) _x (SiO ₂ ) _1-X (0.7 ≦ x ≦
0.85) is good. The thickness of the layer 42 on the reflection / heat dissipation layer side is 5
.About.50 nm, preferably 10 to 30 nm, and the recording layer side layer 41 is suitable to be 10 to 100 nm, preferably 10 to 50 nm.

In the present invention, the reflection / heat dissipation layer 5 is provided on the second protective layer 4. Since the reflection / heat dissipation layer 5 must have the dual roles of a reflection layer and a heat dissipation layer, it is formed of a material having a high reflectance and a high thermal conductivity to some extent.
Specifically, a metal material such as Al, Au, Ag, or an alloy thereof can be used, and among them, Ti, Cr, etc. are 1 to
An Al alloy containing 3% by weight is suitable. Reflective heat dissipation layer 5
Has a thickness of 10 to 300 nm, preferably 50 to 300 nm.
It is 200 nm. When the thickness is less than 10 nm, the function of the reflection and heat dissipation layer 5 is not fulfilled, and when the thickness is more than 300 nm, the sensitivity is lowered and the interface is liable to be peeled off.

Actually, when the optical information recording medium of the present invention is manufactured, the protective layer and the reflection heat dissipation layer are formed by sputtering,
Physical vapor deposition methods such as ion plating, plasma CVD
It can be formed by a method such as chemical vapor deposition. However, the magneto-optical recording medium of the present invention is not limited to those having various layers as described above, and for example, a synthetic resin film as an organic protective film (cover layer) on a reflective layer or the like. They may be provided, or they may be attached by an adhesive.

[0029]

EXAMPLES Next, the present invention will be described more specifically with reference to examples.

Example 1 A PC molded substrate with a pregroup having a diameter of 86 mm and a thickness of 1.2 mm was prepaked in the air at 90 ° C. for 2 hours in advance, and then set in a vacuum chamber of a sputtering apparatus at a vacuum pressure of 5 ×.
It was evacuated to 10 ^-7 Torr or less. Then A
Introducing a mixed gas of r and O ₂ and adjusting the pressure to 3 × 10 ^-2 Tor
After adjusting to r, a ZrO ₂ film having a thickness of about 10 nm was formed by RF magnetron sputtering using metal Zr as a target. Then, (ZnS) ₀ .
₇ was (SiO _{2) 0.} The first protective layer consisting of two layers by forming a _third film of about 190nm thick. Further, as a recording layer, a film containing Ag, In, Sb, and Te as main components is used for about 2
After being formed to a thickness of 0 nm, a second protective layer (ZnS) ₀ .
₈ (SiO _{2) 0.} To form a ₂ layer of about 20nm thick. Finally, an Al alloy film having a thickness of about 50 nm was formed as a reflection / heat dissipation layer, and then it was carried out from the vacuum chamber into the atmosphere to obtain the optical information recording medium of the present invention.

Examples 2 to 18 and Comparative Example 1 The material composition and film thickness of the first protective layer and the second protective layer are as shown in Table 1, and the other conditions are the same as in Example 1 and Example 2
-18 optical information recording media were obtained. On the other hand, except that the first protective layer and the second protective layer are made of the materials and film thicknesses shown in Table 1 and the recording layer is a GeSbTe film (about 20 nm thick),
An optical information recording medium of Comparative Example 1 was obtained in the same manner as in Example 1. In each of the optical information recording media of Examples 2 to 18 and Comparative Example 1, an organic protective layer made of an acrylic UV curable resin was further applied on the reflective heat dissipation layer by a spinner in an amount of 5 to 10 μm and UV cured. .

[0032]

[Table 1]

The 19 types of optical information recording media produced above were evaluated using a pickup having a wavelength of 780 nm and an NA of 0.5. The linear velocity of the optical disk was 1.2 m / s. Overwrite recording of signals of recording frequency 720 kHz and 200 kHz alternately, and C / of the signal of 720 kHz
N and erasure ratio were used as characteristic values. 2 (Example 1) and FIG. 3 (Comparative Example 1) show how the C / N of the signal at 720 kHz changes due to repeated overwriting. In addition, Example 2
The results of Nos. 18 to 18 were similar to those of Example 1. As can be inferred from FIG. 2, by making the first protective layer, the second protective layer and the recording layer as in the present invention, the number of repetitions is improved.

[0034]

According to the present invention, as compared with the prior art, C
It is possible to provide an optical information recording medium which can achieve a dramatic improvement in / N and erasing ratio and which is excellent in repeated recording / erasing characteristics.

[Brief description of drawings]

FIG. 1 is a diagram showing two examples of an optical information recording medium of the present invention.

FIG. 2 is a diagram showing characteristics of the optical information recording medium obtained in Example 1.

FIG. 3 is a diagram showing characteristics of an optical information recording medium obtained in Comparative Example 1.

[Explanation of symbols]

1 plastic substrate 2 first protective layer (21 substrate side layer, 22 recording side layer) 3 phase change type recording layer 4 second protective layer (41 recording layer side layer, 42 reflection heat dissipation layer side layer) 5 reflection Heat dissipation layer

Claims (7)

[Claims] 1. An optical information recording medium in which at least a first protective layer, a phase-change recording layer, a second protective layer and a reflection heat dissipation layer are sequentially provided on a plastic substrate, and the main constituent elements of the phase-change recording layer. Is Ag, In, Sb and Te, and the first protective layer is composed of two layers, of which the layer on the substrate side is an oxide thin film containing O of 30 atom% or more. Information recording medium. 2. The layer on the substrate side of the first protective layer composed of the two layers is (Zr _x Ce _1-x ) _y O _1-y (0 ≦ x ≦ 1, 0.25 ≦
y ≦ 0.4) or Ta _x O _1-x (0.22 ≦ x ≦ 0.3
The optical information recording medium according to claim 1, which is 5). 3. The layer on the phase change recording layer side of the first protective layer composed of the two layers is (ZnS) _x (SiO ₂ ) _1-x (0.7 ≦
The optical information recording medium according to claim 1, wherein x ≦ 0.85). 4. An optical information recording medium in which at least a first protective layer, a phase-change recording layer, a second protective layer, and a reflection heat dissipation layer are sequentially provided on a plastic substrate, and main constituent elements of the phase-change recording layer. Is Ag, In, Sb and Te, and the second protective layer is a compound containing at least Si and N of Si, B, O and N, and N is contained in an amount of 30 atom% or more. Optical recording medium. 5. An optical information recording medium in which at least a first protective layer, a phase-change recording layer, a second protective layer and a reflection heat dissipation layer are sequentially provided on a plastic substrate, and main constituent elements of the phase-change recording layer. Is Ag, In, Sb, and Te, and the second protective layer is composed of two layers, and the layer on the reflection and heat dissipation layer side is a nitride thin film containing 30 atom% or more of N. Optical information recording medium. 6. A compound containing at least Si and N in a layer on the reflection and heat radiation side of the second protective layer consisting of the two layers, where N is 30
content of atom% or more, or B _x N _1-x (0.4
The optical information recording medium according to claim 5, wherein ≦ x ≦ 0.6). 7. The layer on the phase change recording layer side of the second protective layer composed of the two layers is (ZnS) _x (SiO ₂ ) _1-x (0.7 ≦
The optical information recording medium according to claim 5, wherein x ≦ 0.85).