JPH11238253A - Optical information record medium and information recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information record medium having good disk characteristics in a wide range of the line velocity and in a wide range of the power and having excellent storage stability. SOLUTION: This medium consists of a substrate 1, a recording layer 3, protective layers 4, 7 containing sulfur atoms, an intermediate layer 6 adjacent to the protective layers 4. 7, and a reflection layer 5 essentially comprising silver and adjacent to the intermediate layer 6. The intermediate layer 6 in the region adjacent to the reflection layer 5 consists of such elements that do not form compds. with silver and that have <=5 at.% solubility of silver to the elements of the intermediate layer and <=5 at.% solubility of the elements in the intermediate layer to silver, while in the region adjacent to the protective layer, the reflection layer 5 consists of elements having low reactivity with sulfur or such elements that sulfides of these are chemically stable.

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 such as a phase change recording medium and a magneto-optical recording medium.

[0002]

2. Description of the Related Art In recent years, as the amount of information has increased, there has been a demand for an information recording apparatus capable of recording and reproducing a large amount of data at a high density and at a high speed, and a recording medium suitable for the information recording apparatus. It is expected as a medium to respond. Optical discs include a write-once type, which allows recording only once, and a rewritable type, which allows recording / erasing as many times as desired. Examples of the rewritable optical disk include a magneto-optical recording medium utilizing a magneto-optical effect and a phase change recording medium utilizing a change in reflectivity accompanying a reversible change in crystalline state.

The phase-change recording medium has the advantage that recording and erasing can be performed only by modulating the power of laser light without requiring an external magnetic field, and the recording / reproducing apparatus can be downsized. Further, there is an advantage that it is possible to increase the density with a short wavelength light source without changing the material of the recording layer and the like from a medium that can record and erase at a wavelength of about 800 nm which is currently mainstream.

A phase change type recording medium often uses a chalcogen-based alloy thin film as a recording layer material.
bTe system, InSbTe system, GeSnTe system, AgIn
SbTe-based alloys can be used. Layer structure is usually a protective layer,
It has a four-layer structure of a recording layer, a protective layer, and a reflective layer. What is currently in practical use as a rewritable phase-change recording medium,
The crystalline state is an unrecorded / erased state, and the amorphous state is a recorded state.

[0005] Recording, that is, formation of an amorphous mark is performed by heating the recording layer to a temperature higher than the melting point and rapidly cooling the recording layer. Erasing, that is, crystallization, is performed by heating the recording layer to a temperature higher than the crystallization temperature of the recording layer and lower than the melting point. In order to prevent the recording layer from evaporating and deforming due to such heating and cooling, the recording layer is usually sandwiched above and below by a heat-resistant and chemically stable dielectric protective layer to form a sandwich structure. The protective layer promotes thermal diffusion from the recording layer during recording, realizes a supercooled state, contributes to the formation of amorphous marks, and during erasure, keeps the recording layer at a high enough temperature for solid-phase crystallization. Work as a layer.

Further, by providing a metal reflective layer on the upper part of the sandwich structure to form a four-layer structure, heat diffusion is further promoted, and an amorphous mark is formed more stably. A phase-change type recording medium capable of one-beam overwriting, in which the erasing and re-recording processes are performed only by the intensity modulation of one focused light beam, can simplify the layer configuration of the recording medium and the drive circuit configuration. It is attracting attention as an inexpensive and high-density medium for large-capacity recording systems.

[0007] Recently, a CD (Compact Disc) or a DVD (Digi
tal Versatile Disc or Digita Video Disc) has been developed. Rewritable CD (CD-Rewritable, CD-
RW), it is difficult to achieve the current CD standard of a reflectance of 70% or more, but if the reflectance is in the range of 15 to 25%, the compatibility of the recording signal and the groove signal with the CD can be ensured, and the reflectance of the CD can be improved. If an amplification system for covering the low level is added to the reproduction system, compatibility can be ensured in the category of the current CD drive technology.

In the CD-RW, recording in a groove is performed. In this groove, a wobble including address information is used. The meandering is performed at a frequency obtained by frequency-modulating a carrier frequency of 22.05 kHz with address information or the like, and its amplitude (Wobble Amplitude) is very small, about 30 nm, as compared with the groove pitch (1.6 μm). An ATIP signal (Absolute Time In Pre-g) is obtained by frequency-modulating the meandering and incorporating address information of a specific position on a certain track.
roove).

The ATIP signal is a recordable write-once disc (CD-Recordable, CD-R) using an organic dye.
Has already been used. The use of the ATIP signal makes it possible to control the rotation speed of an unrecorded disk, and it is possible to record at a 1 ×, 2 ×, and even 4 ×, 6 × speed of the linear velocity (1.2 to 1.4 m / s) of a CD. Now you can. Actually, a CD-R widely used in the market is generally a medium capable of performing good recording at both double speed and quadruple speed of a CD.

Therefore, even in a CD-RW in which phase change recording is performed, the CD-RW is at least twice as fast as the CD linear velocity (2.4 to 2.8 m).
/ S) to 4 × speed (4.8 m / s to 5.6 m / s), 6 × speed (7.2 m / s to 8.4 m / s), 8 × speed (9.6 m / s to 11.2 m) A medium capable of excellent overwriting at a linear velocity in the range of / s) is desired. On the other hand, a rewritable DVD, which is a higher-density rewritable optical disc, is being actively developed using the same phase change optical recording technology. Here, similarly to the case of the CD-RW, the reference reproduction speed of 3.5 m / s of the read-only DVD is set to 1
There is a need for a medium that can be overwritten in at least a double speed (7 m / s) to a quadruple speed (14 m / s) linear speed range.

That is, the same mark length must be recorded with high quality simply by making the reference clock frequency inversely proportional to the linear velocity even when recording is performed with the linear velocity changed. Further, since a semiconductor laser is used for recording, the recording power cannot be increased so much, and it is preferable that recording can be performed at about 15 mW or less at any linear velocity. However, in the phase change recording medium, if the ratio between the maximum linear velocity and the minimum linear velocity during overwriting is twice or more, normal recording cannot be performed at any linear velocity in many cases.

In general, when the linear velocity at the time of recording is changed, the irradiation power required to raise the temperature of the recording layer to the same temperature is different, and even if the irradiation power is adjusted to make the maximum ultimate temperature of the recording layer the same. However, the same heat history such as the temperature rise / cooling rate and the temperature distribution is not always achieved. At the time of recording, the recording layer is heated and melted once, then cooled at a speed higher than the critical cooling rate to form an amorphous mark, and at the time of erasing, the recording layer is heated and then cooled relatively slowly to crystallize. The cooling rate depends on the linear velocity when using the same layer configuration. That is, at a high linear velocity, the cooling rate increases, and at a low linear velocity, the cooling rate decreases.

That is, at the time of overwriting, as the linear velocity increases, the cooling rate near the melting point also increases, and an amorphous mark is easily formed. Conversely, as the linear velocity decreases, the cooling rate also decreases, which may cause recrystallization during recording. This is apparent from the following simulation results by the present inventors.

ZnS and SiO on a polycarbonate substrate
₂ is 100 nm, a recording layer of Ge ₂ Sb ₂ Te ₅ is 25 nm, a protection layer of ZnS and SiO ₂ is 20 nm, and a reflection layer of Al alloy is 100 nm.
A heat distribution simulation was performed by solving a thermal diffusion equation in a case where recording power and erasing power were applied to the formed disks.

At a position 0.1 μm ahead of the pulse irradiation start point, the recording layer was heated and the cooling rate near the melting point (600 ° C.) in the process of decreasing the temperature after reaching the maximum temperature of 1350 ° C. was examined. 0.9 K / n at a linear velocity of 1.4 m / s
sec, at a linear velocity of 4 m / s, 2.2 K / nsec, linear velocity of 1
At 0 m / s or more, it was several K / nsec or more. on the other hand,
At the time of erasing, it is necessary to raise the temperature of the recording layer to a temperature higher than the crystallization temperature and lower than the melting point, and then keep the temperature above the crystallization temperature for a certain time.
Therefore, when the linear velocity increases, the heat distribution of the recording layer at the light beam irradiation portion becomes relatively sharp temporally and spatially, so that it is difficult to crystallize, and the unerased portion is easily generated.

In order to perform erasing at a high linear velocity, it is necessary to form the recording layer into an alloy having a composition with a high crystallization rate (easy to recrystallize) or a layer structure in which heat cannot escape. On the other hand, in order to perform recording at a low linear velocity, the recording layer must be made of an alloy having a composition with a low crystallization rate or a layer structure in which heat can easily escape.
That is, two types of media are produced according to the linear velocity.

However, it is not preferable to prepare another kind of CD-RW disc for recording at, for example, double speed and quadruple speed of a CD. Similarly, it is not preferable to prepare another type of rewritable DVD medium for recording at 2 × speed and 4 × speed of DVD.

[0018]

In order to solve this problem, it is conceivable to change a pulse strategy at the time of overwriting, that is, a method of dividing and controlling an irradiation beam into pulses according to a linear velocity. This gives 1
A method for obtaining good overwrite characteristics in a linear velocity range from about m / s to about 10 m / s is described in GeTe.
-Sb ₂ Te ₃ present inventors in a phase change recording medium of the pseudo binary alloy system recording layer including have reported several.

However, in general, the variable pulse strategy complicates the pulse generation circuit and the like and increases the manufacturing cost of the drive. Therefore, if possible, the pulse strategy can be changed with a single pulse strategy or as simple as possible. That can cover a wide linear velocity range. In order to solve such problems, the present inventors have previously described the use of a reflective layer having a specific film thickness and volume resistivity in U.S. Patent Application Serial No. 09 / 048,042. It was proposed to use a reflective layer.

It is preferable to use a reflective layer made of a material mainly composed of a metal having high reflectivity and high thermal conductivity such as silver, because it enhances the optical interference effect and the heat radiation effect. High thermal conductivity, 100nm
A sufficient heat radiation effect can be obtained even with the following relatively thin films. Further, it is advantageous in terms of ease of film formation and economy. However, according to further studies by the present inventors, there is a problem that gold and silver do not have very good adhesion to a dielectric.
It has been found that corrosion by sulfur causes particular problems when the protective layer contains sulfur.

Further, the earlier application proposes a multilayer reflective layer in which a first reflective layer made of an aluminum alloy is provided on a protective layer, and a second reflective layer made of silver is provided thereon. However, in this case, mutual atom diffusion occurs between aluminum and silver, and although good recording characteristics can be obtained immediately after film formation, storage stability is poor, and accurate recording can be performed under high temperature and high humidity. It turned out that the problem of disappearing occurs.

That is, when a material containing silver as a main component is actually used as the reflective layer, the storage stability is insufficient. In particular, when recording is performed after long-term storage of the medium in a severe environment, the recording sensitivity is high. And a phenomenon in which the recording signal intensity and the like are changed was observed and found to be a problem. The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical information recording medium having good disc characteristics over a wide linear velocity range and a wide irradiation power range. is there. It is another object of the present invention to provide an optical information recording medium having excellent storage stability.

[0023]

The gist of the present invention is to provide a substrate, a recording layer, a protective layer containing a sulfur atom, an intermediate layer in contact with the protective layer, and a silver as a main component in contact with the intermediate layer. The intermediate layer does not form a compound with silver on the side in contact with the reflective layer, and has a solid solubility of the intermediate layer element in silver and a silver solubility in the intermediate layer element. It is characterized by comprising an element having a solid solubility of 5 atomic% or less, and having a low reactivity with sulfur or an element whose sulfide is chemically stable on the side in contact with the protective layer. Optical information recording medium. Alternatively, the intermediate layer is made of an element that forms a complete solid solution with silver, is a metal or semiconductor oxide, nitride, carbide, or is made of amorphous carbon. Be in the medium.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION First, the present inventors have found that a medium using a combination of a protective layer containing a sulfur atom and a reflective layer containing silver as a main component has no problem in the initial characteristics, but is subjected to repeated recording and long-term storage. It was found that the deterioration was remarkable and that it was difficult to use it practically as it was.

Further, when a layer mainly composed of, for example, aluminum is provided as an intermediate layer between the protective layer containing sulfur atoms and the reflection layer mainly composed of silver, the initial characteristics are no problem, but the storage stability is maintained. It was found that it was poor in performance and deteriorated remarkably by an environmental resistance test, and was not suitable for practical use. Therefore, as a result of various studies on the intermediate layer provided between the protective layer containing a sulfur atom and the reflective layer containing silver as a main component, the storage stability and the repetitive recording characteristics when the intermediate layer satisfies the specific requirements. The present invention has been found to provide a practical medium which is excellent in the present invention.

That is, in the present invention, the intermediate layer does not form a compound with silver on the side in contact with the reflective layer, and has a solid solubility of the intermediate layer element in silver and a silver solubility in the intermediate layer element. The solid solubility of each element is 5 atomic% or less,
On the side in contact with the protective layer, it has a low reactivity with sulfur or its sulfide is made of an element which is chemically stable. Alternatively, the intermediate layer is made of an element that forms a complete solid solution with silver, is a metal or semiconductor oxide, nitride, carbide, or is made of amorphous carbon.

It should be noted that, in the German Patent No. 98782,
A ZnS layer on a glass substrate, a MnBi layer as a ferromagnetic layer,
Although a magneto-optical recording medium in which a ZnS layer and a silver layer are laminated is described, a combination of a protective layer containing a sulfur atom and a reflective layer containing silver as a main component has a problem in repetitive recording characteristics and storage stability. Is not described at all, and there is no suggestion that providing an intermediate layer that satisfies the above specific requirements solves these problems.

JP-A-8-329525 discloses an Au ₅₀ Ag ₅₀ reflective layer and a (ZnS) ₈₀ layer on a polycarbonate substrate.
(SiO ₂ ) ₂₀ protective layer, (Ge ₂ Sb ₂ Te ₅ ) ₉₀ (Cr ₄
Te ₅ ) ₁₀ recording layer, (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer,
A phase-change recording medium in which a Si first reflective layer and an Al ₉₇ Ti ₃ second reflective layer are laminated is described, and Al, Au, Cu, Pt, Pd, Sb-Bi, Ag and its alloys are listed along with their alloys, but there is no description that the combination of a protective layer containing a sulfur atom and a reflective layer containing silver as a main component has a problem in repeated recording characteristics and storage stability. In addition, there is no suggestion that these problems can be solved by providing an intermediate layer satisfying the above specific requirements.

JP-A-9-185846 discloses that a (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, a (Cr ₄ Te ₅ ) ₇ (Ge ₂ Sb ₂ Te ₅ ) ₉₃ recording layer are provided on a polycarbonate substrate,
(ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, Si first reflective layer,
A phase change recording medium in which a tungsten diffusion preventing layer and a second reflective layer of Al _{9 7} Ti ₃ are laminated is described, and Al, Au, Cu, Mo, Ta, W, and C are used as first and second reflective layer materials.
Although Ag and its alloys are listed together with o, Pt and their alloys, etc., they are only examples of many elements, and the use of a material mainly composed of silver as a reflective layer and its usefulness are described. Not. Therefore, there is no description that the combination of the protective layer containing a sulfur atom and the reflective layer containing silver as a main component has a problem in repetitive recording characteristics and storage stability. There is no indication that these problems will be solved.

The optical information recording medium of the present invention includes:
Although various types of recording media such as a magneto-optical recording medium and a phase change recording medium can be adopted, preferably a phase change recording medium,
In particular, it is a phase change type recording medium utilizing a difference in reflectance between a crystalline state and an amorphous state. Hereinafter, the present invention will be described with respect to a phase change recording medium as a preferred example. Conventional phase-change optical disks and the like have a protective layer, a recording layer, a protective layer,
The reflection layer is provided in this order mainly using a sputtering method,
Further, a structure in which an ultraviolet curable resin layer is provided thereon is mainly used. The reflection layer is provided to increase the signal amplitude by more actively using the optical interference effect and to function as a heat dissipation layer. In the case of a phase change recording medium, the reflection layer This is because a supercooled state required for formation is easily obtained. For this reason, a metal having high reflectance and high thermal conductivity is generally desirable for the reflective layer, and specific examples thereof include Au, Ag, and Al.

Ag is preferable in terms of ease of film formation and economy. The price as a sputtering target is relatively low, the discharge is stable, the deposition rate is fast, and it is stable in air,
In addition, it exhibits excellent characteristics in terms of reflectance and thermal conductivity. Of course, a similar effect can be expected even in a system in which a small amount of impurities are mixed with Ag. However, a film provided in contact with Ag is often incompatible with Ag. For example, when a layer containing an element which is easily diffused is in contact with the Ag film, the thermal conductivity may be significantly reduced. In this case, when a new signal is to be recorded, phenomena such as a change in recording sensitivity due to a difference in heat distribution at the time of recording and a poor signal characteristic because a mark is not formed clearly are undesirable.

Therefore, in a conventional phase-change optical disk or the like, A
g, Ta, Ti, Cr, M
An Al alloy containing 0.5 to 5 atomic% of o, Mg, Zr, V, Nb, or the like was generally used as the reflective layer. However, even in that case, the same phenomenon occurs to some extent after storage in a severe environment. If the recording layer is Ma _w (Sb _z Te _1-z ) _1-w
Alloy thin film (however, 0 ≦ w ≦ 0.3, 0.5 ≦ z ≦ 0.
9, Ma is In, Ga, Zn, Ge, Sn, Si, C
u, Au, Ag, Pd, Pt, Pb, Cr, Co, O,
N, S, Se, Ta, Nb, V, Bi, Zr, Ti, M
n, Mo, Rh and at least one element selected from the group consisting of rare earth elements) are particularly important because differences in heat distribution are easily reflected in the mark shape.

Elements that easily diffuse into Ag include, for example, A
1, S, etc. Therefore, for example, ZnS-SiO often used as a protective layer in a phase change optical disk
In the case of using ₂ includes a recording characteristic provided in contact with ZnS-SiO ₂ protective layer as in the conventional structure of said Ag reflective layer is changed with time. In addition, many defects that can be observed with a microscope from the Ag side appear, and even if the disk has not elapsed, if recording is repeated, the recording characteristics deteriorate after about 100 times, so that the disk is not usable.

Therefore, the present inventor has considered providing a reflective layer containing Ag as a main component with an intermediate layer which prevents diffusion from the protective layer and at the same time does not hinder the heat conductivity or the like in practical use. It is. The phase change recording medium of the present invention comprises a substrate, a phase change recording layer, a protective layer and a reflective layer, and has an intermediate layer in contact with the protective layer and the reflective layer. For example, a lower protective layer, a phase-change recording layer, an upper protective layer, an intermediate layer, and a reflective layer are provided on a substrate in this order. By adopting this layer configuration and performing recording and reproduction through the substrate, errors due to scratches and dust on the substrate can be considerably prevented, and the reliability of the medium can be improved.

Alternatively, a reflective layer, an intermediate layer, a protective layer, a phase-change recording layer, and a protective layer are provided on a substrate in this order. Alternatively, these layers may be provided on both sides of the substrate. By taking this layer configuration and performing recording / reproduction without passing through the substrate, the distance between the optical head and the recording layer can be extremely reduced using a floating type head or a contact type head, and the recording density of the medium can be increased. Can be improved.

In the case where the intermediate layer is formed of a specific metal or alloy, the intermediate layer does not form a compound with silver on the side in contact with the reflective layer, and the solid solubility of the intermediate layer element in silver and the The intermediate layer is made of an element having a silver solid solubility of 5 atomic% or less, and has a low reactivity with sulfur or a chemically stable sulfide on the side in contact with the protective layer. Consists of elements.

Here, the conditions to be satisfied by the elements forming the intermediate layer are basically determined by referring to a binary alloy phase diagram of silver or sulfur and the elements forming the intermediate layer. Authoritative publications for such binary alloy phase diagrams include the "Constitution of Binary Alloy
s ", (Max Hansen and Kurt Anderko, second edition (1
985), Genium Publishing Corporation, New York).

Silver easily diffuses into other metals even at a low temperature of less than 100 ° C., and the formation of a solid solution or a compound due to such diffusion generally impairs the high reflectance and high thermal conductivity that silver originally has. Is not preferred. Therefore, the side of the intermediate layer which is in contact with the reflective layer must first be made of an element which does not form a solid solution or compound with silver. In the present invention, the phrase that an element does not form a solid solution with silver means that the element does not form a solid solution with silver at all, and that the solid solubility in silver and the solid solubility of silver in the element are 5 atomic% or less. It is difficult to dissolve in silver.

Here, the solid solubility refers to the maximum solid solubility in all temperature ranges as long as it is in a solid state. the above,
In the binary alloy phase diagram by Hansen, elements that do not form a solid solution with silver and do not form a compound include, specifically, sodium, lead, bismuth, silicon, tantalum, cobalt, chromium, tungsten, and vanadium. No.

Of these, sodium, lead, and bismuth exist at a relatively low temperature of eutectic temperature of 500 ° C. or less, and have a somewhat poor thermal stability. That is, according to the phase diagram, the eutectic temperatures are sodium (97 ° C.), lead (304 ° C.), bismuth (262 ° C.), silicon (830 ° C.), and chromium (961 ° C.).
° C). Although a detailed phase diagram is not described for tantalum, cobalt, tungsten, and vanadium, it is known that silver is almost insoluble even in a molten state without a compound present. Nickel has little solid solubility in silver, and there appears to be only a small amount of silver in nickel, but well below 5 atomic%.

Sodium is less preferred because of its atmospheric instability. Meanwhile, zirconium,
Magnesium, manganese, indium, titanium, antimony, germanium, tellurium, zinc and the like are not suitable because they form compounds with silver or form solid solutions in a wide range of concentrations. Also, aluminum forms a solid solution with silver, and thus is not preferable as an intermediate layer element on the side in contact with silver.

With respect to the stability of the film interface when silver (elements of silicon, tantalum, cobalt, chromium, tungsten, and vanadium) and silver, which are considered to be preferable according to the above guidelines, are laminated, a laminated film of thin films is actually formed and accelerated. It was confirmed by a test, and it was confirmed that the heat dissipation effect was not reduced due to the change in thermal conductivity due to alloying. Among these elements, in particular, tantalum and nickel are the most preferable elements in which peeling due to internal stress of the film hardly occurs.

However, even in the case of an element that forms a solid solution with silver, when a complete solid solution is formed, phase separation does not occur, so that the element has little effect on the thermal conductivity. Preferable examples of forming a complete solid solution with silver include gold and palladium. On the other hand, the intermediate layer, on the side in contact with the sulfur-containing protective layer, is an element having low reactivity with highly corrosive sulfur, that is, an element which does not form a compound with sulfur at all in the phase diagram, or has a sulfide at the interface. Even when a substance is formed, the sulfide itself is chemically stable and passive, and is made of an element having a diffusion preventing effect.

The stability of the sulfide can be confirmed in the literature or by actually measuring the thermogravimetric loss spectrum.
From the Hansen phase diagram, it is understood that aluminum is a rare element that does not form a compound with sulfur at all and is most preferable. Silicon, tantalum, tungsten, germanium and vanadium are SiS ₂ , TaS ₂ ,
It is thought that WS ₂ , GeS ₂ , and V ₂ S ₃ are mainly formed, but at temperatures higher than 500 ° C., thermogravimetric changes such as melting, decomposition, and sublimation occur.

Cobalt and chromium form a large number of sulfides, and the melting point and decomposition temperature of the sulfides themselves are higher than 500 ° C. in the phase diagram. These elements are represented by ZnS: Si
The stability was confirmed experimentally by forming a film on the O ₂ protective layer.
At least no corrosion due to the progress of the sulfidation reaction was observed, and the reflectance did not change. Ag ₂ S, a sulfide of silver and copper
According to the phase diagram, the compound itself and Cu ₂ S seem to be thermally stable, but experimentally showed some instability on the ZnS: SiO ₂ protective layer. The phase diagram shows a phase transformation in a solid phase at 500 ° C. or lower, which is considered to be not always stable.

Finally, when the intermediate layer is made of a compound, the intermediate layer is made of a metal or semiconductor oxide, nitride, carbide, or amorphous carbon. These are themselves stable compounds. When the phase change medium is used as the recording layer, it is preferably a heat-resistant compound having a melting point of 1000 ° C. or higher. Sulfides are not preferred because of their reactivity with silver.

It is desirable for the intermediate layer to be a compound transparent to the wavelength of the light source used for optical recording or reproduction in order to effectively utilize the high reflectance of silver. In this regard, hydrogenated amorphous carbon having high transparency is preferable as amorphous carbon. The reflective layer contains silver as a main component. Mainly containing silver means that silver is contained at 70 atomic% or more. Preferably, silver is contained in an amount of 95 atomic% or more, more preferably 98 atomic% or more. Particularly preferably, the reflective layer is made of Ti, V, T
a, Nb, W, Co, Cr, Si, Ge, Sn, Sc,
It is made of pure silver or a silver alloy containing at least one element selected from the group consisting of Hf, Pd, Rh, Au, Pt, Mg, Zr, Mo and Mn in an amount of 0.2 at% to 2 at%.

On the other hand, the protective layer contains sulfur, and preferably contains sulfides such as zinc sulfide, tantalum sulfide and rare earth sulfide. Containing 20 to 90 mol% of these,
A mixed film containing a heat-resistant compound having a melting point or a decomposition temperature of 1000 ° C. or more, that is, oxides, nitrides, fluorides, and carbides of metals and semiconductors is particularly desirable. The thickness of the intermediate layer is usually at least 10 °, preferably at least 50 °, while it is usually at most 1000 °, preferably at most 500 °, more preferably at most 200 °, in order to effectively function the high thermal conductivity of silver. .

The intermediate layer is composed of one or more layers. Among them, preferred embodiments of the intermediate layer include the following two embodiments. Aspect (1): The intermediate layer is composed of two layers: a layer containing aluminum as a main component and a diffusion prevention layer for preventing alloying of aluminum and silver. The former layer is in contact with the protective layer, and the latter layer is Contact with reflective layer. Aspect (2): The element constituting the intermediate layer does not form a compound with silver, and both the solid solubility of the intermediate layer element in silver and the solid solubility of silver in the intermediate layer element are 5 Atomic% or less of the element, and further, an element whose reactivity with sulfur is low or whose sulfide is chemically stable. Alternatively, the intermediate layer is made of an element that forms a complete solid solution with silver, is a metal or semiconductor oxide, nitride, carbide, or is made of amorphous carbon.

First, the mode (1) will be described. Aspect (1) is generally expressed as follows. A first reflective layer, a diffusion preventing layer, and a volume resistivity of 20 nΩ on the protective layer;
A second reflective layer having a thickness of not less than m and not more than 80 nΩ · m is provided. In this case, the layer containing aluminum as a main component corresponds to the first reflection layer, the layer for preventing alloying of aluminum and silver corresponds to the diffusion prevention layer, and the reflection layer corresponds to the second reflection layer.

Here, the reason why the aluminum which reacts with silver to form a solid solution and dare to use a diffusion prevention layer between silver and aluminum will be described below. An object of the present invention is to obtain a stable optical recording medium while effectively utilizing the high thermal conductivity of silver. For that purpose, an intermediate layer provided between a protective layer and a silver reflective layer has a high thermal conductivity. It is desirable that In addition, it is preferable that the intermediate layer itself has a high reflectance because the intermediate layer and the silver reflection layer function as a reflection layer having a high reflectance and a high thermal conductivity as a whole.

Aluminum is the most preferable material in terms of reflectance, thermal conductivity, and chemical stability, besides the reactivity with silver, and is highly useful even if a diffusion preventing layer is provided. According to this configuration, even if an intermediate layer is provided between the protective layer and the reflective layer, the thermal conductivity is hardly affected, and the disk has good disk characteristics over a wide range of linear velocities and a wide range of power, and A medium excellent in storage stability can be obtained, which is extremely preferable in practical use.

Hereinafter, the embodiment (1) will be described based on this generalized embodiment. The medium of the embodiment (1) is shown in FIG.
As shown in the figure, usually, the substrate 1 / lower protective layer 2 / phase change type recording layer 3 / upper protective layer 4 / first reflective layer 5 / diffusion prevention layer 6
/ The second reflective layer 7. It is desirable that the surface is covered with an ultraviolet or thermosetting resin (protective coat layer 8).

In the embodiment (1), the phase change type recording layer 3
Various conventionally known materials can be used as the material of Ge.
SbTe, InSbTe, AgSbTe, AgInSb
Te, AgGeSbTe, etc. can be exemplified, but an alloy mainly composed of an SbTe alloy near the eutectic point of Sb ₇₀ Te ₃₀ which is stable in both crystalline and amorphous states and capable of high-speed phase transition between the two states is available. Most preferred. This is because segregation hardly occurs when overwriting is repeatedly performed, and it is the most practical material. A particularly preferred composition of the phase-change recording layer 3 is M
a _w (Sb _z Te _1-z ) _1-w alloy (where 0 ≦ w ≦ 0.
3, 0.5 ≦ z ≦ 0.9, Ma is In, Ga, Zn, G
e, Sn, Si, Cu, Au, Ag, Pd, Pt, P
b, Cr, Co, O, N, S, Se, Ta, Nb, V,
Bi, Zr, Ti, Mn, Mo, Rh and at least one element selected from rare earth elements). More preferably, 0 ≦ w ≦ 0.2 and 0.6 ≦ z ≦ 0.8.
According to the study of the present inventors, the linear velocity dependence is determined by the main components Sb and Te. In the vicinity of the Sb ₇₀ Te ₃₀ eutectic point, the crystallization rate tends to increase as the Sb / Te ratio increases. is there.

The ternary material to which Ge or In is added in the vicinity of the eutectic composition has been widely used in the conventional overwriting with a specific recording pulse pattern.
_{Te-Sb 2 Te 3, InTe} -Sb 2 Te 3 is less degraded than the pseudo binary alloy vicinity material, or a small jitter of mark edge when the mark length recording, is an excellent material. Further, the crystallization temperature is high and the stability over time is excellent.

Since the recording layer is usually amorphous immediately after film formation, it is preferable to crystallize the entire recording layer to be in an initialized state (unrecorded state) as described later. In the aspect (1), a medium capable of excellent overwriting at a wide linear velocity and having a ratio of the minimum linear velocity to the maximum linear velocity at the time of recording at least twice or more is provided. As a more specific example,
At least twice the CD linear velocity (2.4 to 2.8 m / s)
From 4x speed (4.8m / s to 5.6m / s) or D
1x speed (3.5m / s) to 2x speed (7m /
A good overwritable medium is provided in the range of s).

For this reason, the composition of the recording layer is initially 10 m / s
The crystallization speed must be so fast that erasure can be performed sufficiently at a near high speed. As described above, the recording layer of the embodiment (1) is preferably based on the eutectic composition of Sb ₇₀ Te _30, but the linear velocity dependency is affected by the Sb / Te ratio. Therefore, the composition of the recording layer is a Ma _w (Sb _z Te _1-z ) _1-w alloy (where 0 ≦
w ≦ 0.3, 0.5 ≦ z ≦ 0.9, Ma is In, Ga,
Zn, Ge, Sn, Si, Cu, Au, Ag, Pd, P
t, Pb, Cr, Co, O, N, S, Se, Ta, N
b, V, Bi, Zr, Ti, Mn, Mo, Rh and at least one selected from rare earth elements).

As a more specific and preferred example, Mbα
₁ Inβ ₁ Sbγ ₁ Teη ₁ (However, 0.03 ≦ α1 ≦
0.1, 0.03 ≦ β1 ≦ 0.08, 0.55 ≦ γ1 ≦
0.65, 0.25 ≦ η1 ≦ 0.35, 0.06 ≦ α1
+ Β1 ≦ 0.13, α1 + β1 + γ1 + η1 = 1, Mb
Is at least one of Ag and Zn).

More preferably, in the above composition, 0.1.
03 ≦ α1 ≦ 0.1, 0.05 ≦ β1 ≦ 0.08, 0.
6 ≦ γ1 ≦ 0.65, 0.25 ≦ η1 ≦ 0.30, 0.
06 ≦ α1 + β1 ≦ 0.13, α1 + β1 + γ1 + η1
= 1. In this composition range, 10
A sufficient erase ratio can be obtained at the time of overwriting up to near m / s. Further, it can be used as a composition having excellent stability over time.

In has the effect of increasing the crystallization temperature and improving the stability over time. In order to ensure the storage stability at room temperature, In is preferably added at 3 atomic% or more, but 8 atomic% is preferable.
If it is contained in excess of, phase separation is likely to occur, and segregation is likely to occur due to repeated overwriting. More preferably, it is 5 atomic% or more and 8 atomic% or less. Ag or Zn facilitates initialization of the amorphous film immediately after film formation. Although it depends on the initialization method, addition of 10 atomic% or less is sufficient, and if it is too much, stability over time is rather deteriorated, which is not preferable.

In addition, Ag or Zn and In
If it exceeds atomic%, segregation is apt to occur during repeated overwriting, which is not preferable. As another example of a suitable recording layer, Mc _v Ge _y (Sb _x Te _1-x ) _1-yv (where 0.
6 ≦ x ≦ 0.8, 0.01 ≦ y ≦ 0.15, 0 ≦ v ≦
0.15, 0.02 ≦ y + v ≦ 0.2, and Mc is at least one of Ag and Zn).

According to this composition, the aforementioned MbInSbT
It is possible to improve the ease of precipitation of the low melting point metal In and the In-containing alloy in the e-alloy. But on the other hand, G
With the addition of e, the initialization process rapidly takes time. In order to overcome both the easiness of precipitation of In and the difficulty of initialization by Ge, Mdα ₂ Inβ ₂ Ge
δ ₂ Sbγ ₂ Teη ₂ (provided that 0.01 ≦ α2 ≦ 0.
1, 0.001 ≦ β2 ≦ 0.1, 0.01 ≦ δ2 ≦ 0.
1, 0.5 ≦ γ2 ≦ 0.7, 0.25 ≦ η2 ≦ 0.4,
0.03 ≦ β2 + δ2 ≦ 0.15, α2 + β2 + δ2 +
(γ2 + η2 = 1, Md is at least one of Ag and Zn).

The thickness of the phase change type recording layer 3 is generally 10
The range is preferably from 100 nm to 100 nm. If the thickness is less than 10 nm, it is difficult to obtain a sufficient optical contrast, and the crystallization speed tends to be slow, so that erasing in a short time tends to be difficult. On the other hand, if it exceeds 100 nm, it is still difficult to obtain optical contrast, and cracks are likely to occur.

Particularly, in order to obtain a contrast sufficient to obtain reproduction compatibility with a CD or a DVD, the thickness is more preferably from 10 nm to 30 nm. If the thickness is less than 10 nm, the reflectance becomes too low, and if the thickness is more than 30 nm, the heat capacity tends to be large and the recording sensitivity tends to be poor. Further, the volume change accompanying the phase change of the recording layer becomes larger as the recording layer becomes thicker, and microscopic deformation due to repeated overwriting tends to accumulate.
From this viewpoint, the upper limit of the thickness of the recording layer is 30 nm or less, and more preferably 25 nm or less.

As described above, it is preferable to adjust the composition of the recording layer to high-speed overwriting. If a composition that can be sufficiently erased at a high linear velocity is used, a good amorphous mark is hardly formed when recording at a low linear velocity because the recording layer once melted is easily recrystallized. Conventional GeTe-S
In the b ₂ Te ₃ system, in order to obtain a sufficient cooling rate of the recording layer at a low linear velocity, the “quenching structure” in which the thickness of the upper protective layer 4 is small is used.
And it was generally 20 nm to 30 nm.

This trend is prominently shown, for example, in the announcement of the Phase Change Recording Society held annually since 1991 (published by the Japan Society of Applied Physics, sponsored by the Phase Change Recording Society). . The greatest reason is that heat radiation to the reflective layer is effectively applied. In a so-called quenching structure, a high erasing ratio is realized by high-speed crystallization while avoiding the problem of recrystallization by adopting a layer configuration that promotes heat radiation and increases the cooling rate when the recording layer is re-solidified.

Therefore, if the thickness of the upper protective layer 4 is too large, the time for the heat of the recording layer 3 to reach the reflective layer becomes longer,
It has been said that the heat dissipation effect of the reflective layer does not work effectively. The present inventors have found that the linear velocity dependency can be further improved by combining a reflective film having high thermal conductivity with the upper protective layer 4 having a thickness of 30 nm or more and 60 nm or less, as compared with the conventional quenching structure. More preferably 35
nm or more and 55 nm or less.

This is explained as follows with reference to FIG. For recording, it is necessary to raise the temperature of the recording layer above the melting point. However, since a finite time is required for heat conduction, in the process of raising the temperature (the initial several tens of nanoseconds or less), The heat conduction is not remarkable, and the temperature distribution is almost determined only by the heat conduction in the film thickness direction (FIG. 3A).

Therefore, when the temperature of the leading end of the recording mark is first raised to a predetermined temperature, the heat conduction in the film thickness direction is effective. On the other hand, when it is several tens of nanoseconds or more after the start of temperature rise, as shown in FIG. 3B, a planar change in temperature distribution due to lateral heat conduction becomes important. This is because the thickness direction is a problem of thermal diffusion at a distance of at most 0.1 μm,
This is because the plane direction is a problem of thermal diffusion on the order of 1 μm.

In particular, the cooling rate of the recording layer which governs the amorphization process depends on this plane distribution, and the linear velocity dependence of the cooling rate is governed by this plane temperature distribution. At low linear velocities, the scanning speed of the light beam is slow, so that the laser beam proceeds while heating the peripheral portion even during the same irradiation time, and the effect of heat conduction in the planar direction is large. Further, even in the rear end portion of the long mark irradiated with the recording light beam for a relatively long time, the influence of the heat conduction in the plane direction is large.

Therefore, in order to perform mark length recording in a wide linear velocity range in which the ratio of the maximum linear velocity to the minimum linear velocity at the time of recording becomes twice or more, it is necessary to simply perform the temperature distribution in the film thickness direction or the time dependence. It is necessary to accurately control not only the characteristics but also the distribution in the plane direction and the time change. In FIG. 3 (b), lowering the thermal conductivity of the upper protective layer and giving it an appropriate thickness can provide a certain delay effect on the flow of heat to the reflective layer, and the temperature distribution in the plane direction Is easier to control.

The conventional so-called “quenching structure” has not paid sufficient attention to this effect of delaying heat conduction. In the present invention, it is desirable that the material of the upper protective layer 4 has a low thermal conductivity in order to sufficiently exhibit the effect of delaying the thermal conduction. For example, ZnS, ZnO, TaS ₂ or rare earth sulfide is used alone or as a mixture in an amount of 20 mol%. It is preferable that the content be contained at least 90 mol%. Further, a composite dielectric containing a heat-resistant compound having a melting point or a decomposition temperature of 1000 ° C. or more is also desirable.

More preferably, a composite dielectric containing 50 mol% to 90 mol% of rare earth sulfides such as La, Ce, Nd and Y, or a composite dielectric containing 70 to 90 mol% of ZnS, ZnO or rare earth sulfide is used. desirable.
As a heat-resistant compound material having a melting point or a decomposition point of 1000 ° C. or more, Mg, Ca, Sr, Y, La, Ce, Ho,
Er, Yb, Ti, Zr, Hf, V, Nb, Ta, Z
Oxides such as n, Al, Si, Ge, and Pb, nitrides, carbides, and fluorides such as Ca, Mg, and Li can be used.

In particular, as a material to be mixed with ZnO, a sulfide of a rare earth such as Y, La, Ce, Nd or a mixture of a sulfide and an oxide is preferable. SiO ₂ , Ta
A thin film mainly composed of ₂ O ₅ , Al ₂ O ₃ , AlN, SiN or the like tends to have an undesirably high thermal conductivity of itself. In particular, the upper protective layer preferably contains sulfur, and particularly preferably contains sulfides such as ZnS, TaS ₂ , and rare earth sulfides.

The film density of these protective layers is 8 in the bulk state.
0% or more is desirable in terms of mechanical strength. When a mixture dielectric thin film is used, the following theoretical density is used as the bulk density. ρ = Σmiρi (1) mi: molar concentration of each component i ρi: single bulk density The upper protective layer 4 also has an effect of preventing mutual diffusion between the recording layer 3 and the reflective layer 5.

As described above, the thickness of the upper protective layer 4 is usually 30 nm to 60 nm, preferably 35 nm to 5 nm.
The thickness is set to 5 nm or less. If the film thickness is less than 30 nm, a sufficient heat conduction delay effect cannot be obtained, and if it exceeds 60 nm, a sufficient heat radiation effect to the reflective layer cannot be obtained, and plastic deformation due to a heat cycle at the time of repeated overwriting inside the protective layer. It tends to accumulate and deteriorate with the number of overwrites.

In the mode (1), when the effect of delaying the heat conduction by the upper protective layer 4 is obtained, if the upper protective layer is simply thickened, the cooling rate becomes too low. In order to obtain the effect, a reflective layer having a particularly high thermal conductivity is used. However, measuring the thermal conductivity of a thin film such as the reflective layer of the present invention is quite difficult, and has a problem in reproducibility.

In general, the thermal conductivity of a thin film is largely different from the thermal conductivity in a bulk state, and is generally small. Especially 4
In the case of a thin film having a thickness of 0 nm or less, the thermal conductivity may be reduced by one digit or more due to the effect of the island structure at the initial stage of growth, which is not preferable. Therefore, in the present invention, the electric resistance of the reflection film is used as an index instead of the thermal conductivity. In a material in which electrons mainly control heat or electric conductivity, such as a metal film, the thermal conductivity and the electric conductivity have a good proportional relationship, so that the quality of the heat conduction can be estimated using the electric resistance. .

The electrical resistance of a thin film is represented by a resistivity value standardized by its film thickness or the area of a measurement region. For example, the volume resistivity and the sheet resistivity can be measured by the usual four-probe method.
K7194. This makes it possible to obtain much simpler and more reproducible data than actually measuring the thermal conductivity itself of the thin film. Note that the lower the volume resistivity, the higher the thermal conductivity.

In the mode (1), preferably, the reflection layer is made of a first reflection layer mainly composed of aluminum having a thickness of 5 nm to 50 nm, and a first reflection layer having a thickness of 40 nm to 200 nm.
m and a volume resistivity of 20 nΩ · m or more and 80 nΩ · m or less. That is, at least one layer is configured so as to substantially control the heat radiation effect as the low volume resistivity material, and to contribute to the improvement of corrosion resistance, adhesion to the protective layer, and hillock resistance.

In particular, when the upper protective layer contains sulfide, A
Such a configuration is desirable because it is highly corrosive to metals such as g. The thickness of the first reflection layer is preferably 5 nm or more and 50 nm or less. If it is less than 5 nm, the protective effect is insufficient, and if it exceeds 50 nm, the heat radiation effect to the second reflective layer tends to be sacrificed.

The thickness of the second reflection layer is preferably set to 40 nm or more and 200 nm or less. If it is less than 40 nm, the heat radiation effect tends to be insufficient. On the other hand, if it exceeds 200 nm, cracks are likely to occur, and the film formation time tends to be long, and the productivity tends to decrease. Note that a third reflective layer may be further provided on the second reflective layer in order to improve optical characteristics. In this case, the third reflective layer may be made of a material having a high volume resistivity.

Generally, a volume resistivity of 20 nΩ · m or more and 1
If it is 50 nΩ · m or less, it can be used as a reflective layer having high thermal conductivity. Materials having a volume resistivity of less than 20 nΩ · m are substantially difficult to obtain in a thin film state. Volume resistivity 150nΩ
When the volume resistivity is larger than m, for example, 300 nm
If the thickness is larger than the thickness, the sheet resistivity can be reduced. However, according to the study of the present inventors, a sufficient heat radiation effect can be obtained even if only the sheet resistivity is reduced in such a material having a high volume resistivity. I couldn't. It is considered that a thick film increases the heat capacity per unit area.

Further, such a thick film is not preferable from the viewpoint of manufacturing cost because it takes a long time to form the film and increases the material cost. Therefore, when the film thickness is 300 nm or less, the sheet resistivity is 0.1 mm.
It is preferable to use a material having a low volume resistivity of 2 or more and 0.9 Ω / □ or less. Therefore, the first reflective layer containing aluminum as a main component is provided for the purpose of improving corrosion resistance, adhesion to the protective layer, and hillock resistance. However, if the thermal conductivity is too high, the heat radiation effect of the second reflective layer is obtained. Because it is hard to be
Preferably, the volume resistivity is 20 nΩ · m or more and 150 nΩ · m.
The following is assumed.

From the viewpoint of adhesion and reactivity with sulfur, the first
The reflecting layer contains aluminum in an amount of 95 atomic% or more, more preferably 98 atomic%. Particularly preferably, Ta, T
i, Co, Cr, Si, Sc, Hf, Pd, Pt, M
An aluminum alloy or pure aluminum containing at least one element selected from the group consisting of g, Zr, Mo, and Mn in an amount of 0.2 atomic% or more and 2 atomic% or less. In the former, in particular, it is known that the volume resistivity increases in proportion to the concentration of the added element, and that the hillock resistance is improved (Journal of the Japan Institute of Metals, Vol. 59 (1995), pp. 673-678, J. .Vac.Sci.Tec
h., A14 (1996), pp. 2728-2735), durability, volume resistivity, film formation rate, etc. can be used.

When the amount of the added impurity is less than 0.2 atomic%, the hillock resistance is often insufficient, depending on the film forming conditions. On the other hand, if it exceeds 2 atomic%, the above low resistivity may not be obtained. When the aging stability is more important, Ta or Ti, particularly Ta is preferable as the additive component.

Further, an Al—Mg—Si alloy containing 0.3 to 0.8% by weight of Si and 0.3 to 1.2% by weight of Mg is also preferable. In the aspect (1), the volume resistivity of the second reflective layer containing silver as a main component is not less than 20 nΩ · m and not more than 80 nΩ · m. As the thin film having a volume resistivity of 20 nΩ · m or more and 80 nΩ · m or less, preferably, Ti, V, Ta, Nb, W, Co, Cr, S
i, Ge, Sn, Sc, Hf, Pd, Rh, Au, P
A silver alloy containing at least one atom selected from the group consisting of t, Mg, Zr, Mo, and Mn in an amount of 0.2 atomic% or more and 2 atomic% or less, or pure silver is used.

When more importance is placed on the stability over time, Ti, Pd, and Mg are particularly preferable as the additional components. A described above
The volume resistivity of 1 and Ag increases in proportion to the impurity concentration. It is considered that the addition of impurities generally reduces the crystal grain size, increases electron scattering at the grain boundaries, and lowers the thermal conductivity. Adjusting the amount of added impurities is necessary to increase the crystal grain size to obtain the original high thermal conductivity of the material.

The reflection layer is usually formed by a sputtering method or a vacuum evaporation method. The total impurity amount including the amount of moisture and oxygen mixed during the film formation is reduced in addition to the impurity amount of the target and the evaporation material itself. It is necessary to be 2 atomic% or less. Therefore, the ultimate vacuum of the process chamber is 1 × 10
It is desirable that the pressure be ⁻³ Pa or less.

When the film is formed at a ^{pressure of} 1 × 10 ⁻⁴ Pa or less, the film formation rate is 1 nm / sec or more, preferably 10 nm / sec.
/ Sec or more to prevent impurities from being taken in. Alternatively, when intentionally added elements are contained in an amount of more than 1 atomic%, it is desirable to set the film formation rate to 10 nm / sec or more to prevent the addition of additional impurities as much as possible.

Conditions such as the film forming pressure may also affect the crystal grain size. For example, in an alloy film in which about 2 atomic% of Ta is added to Al, an amorphous phase is mixed between crystal grains, and the ratio of the crystalline phase to the amorphous phase depends on film forming conditions. As the sputtering is performed at a lower pressure, the proportion of the crystal part increases, and the volume resistivity decreases (the thermal conductivity increases).

The method of manufacturing the alloy target used for sputtering and the sputtering gas (Ar, Ne, Xe, etc.) also affect the impurity composition or crystallinity in the film. Therefore, even if the above Al alloy composition is disclosed as a material for the reflective layer (Japanese Unexamined Patent Publication No.
1338, JP-A-1-169571, JP-A-1-208744, etc.), the volume resistivity layer configuration shown in the present application is not always shown.

In order to obtain a high thermal conductivity, it is desirable to reduce the amount of impurities as described above.
Since pure metals such as 1 and Ag tend to be inferior in corrosion resistance and hillock resistance, the optimum composition is determined in consideration of the balance between the two. However, it has been found that the medium having the two-layer reflective layer has a problem that storage stability is poor if it is used as it is. If it is kept under high temperature and high humidity, recording cannot be performed at all.

The Auger depth profile showed that both reflective layers were alloyed. As described above, the thermal conductivity of a metal decreases when an impurity is added. A
When alloying of 1 and Ag occurs, the thermal conductivity rapidly deteriorates, so that a rapid cooling rate required for forming an amorphous mark cannot be obtained, and recording becomes impossible.

Therefore, in the mode (1), a material mainly composed of aluminum is used for the first reflection layer and a material mainly composed of silver is used for the second reflection layer. It is preferably a layer that prevents diffusion with silver. Materials for the diffusion prevention layer include metals,
A semiconductor, a metal oxide, a metal nitride, a metal carbide, a semiconductor oxide, a semiconductor nitride, a semiconductor carbide, carbon, or the like can be used. Examples of the metal that can be used as the diffusion preventing layer include at least one selected from the group consisting of Ta, Ni, Co, Cr, Si, W, and V. Among them, Ta and / or Ni are preferable.

The metal, semiconductor oxide, nitride or carbide which can be used as the diffusion preventing layer is selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, tantalum oxide, cerium oxide, lanthanum oxide and yttrium oxide. At least one kind is mentioned. Examples of the amorphous carbon that can be used as the diffusion preventing layer include amorphous hydrogenated carbon. A particularly preferred material is a compound of oxygen and / or nitrogen with the material used for the first and second reflective layers. Tantalum is also a particularly preferred material. In a particularly preferred embodiment, a material mainly containing aluminum is used for the first reflection layer, a material mainly containing silver is used for the second reflection layer, and a material made of aluminum oxide or tantalum is used as the diffusion preventing layer.

The diffusion preventing layer can be formed by ordinary sputtering, but is preferably formed by the following method. After the first reflective layer is formed, the in-line vacuum is broken once and the disk is opened to the atmosphere, whereby a natural oxide film of oxygen (or moisture) in the air and the first reflective layer material is formed on the first reflective layer of the disk. . Thereafter, the disk is returned while the vacuum is evacuated again, and the second reflective layer is formed by film formation such as sputtering. Thereby, the diffusion preventing layer can be easily provided. In order to promote natural oxidation in the air and obtain a sufficient thickness of the diffusion preventing layer in a short time, ozone treatment in the air is also effective.

When the diffusion preventing layer is provided in this way, the diffusion of the first reflection layer and the second reflection layer is suppressed by the oxide layer which is the interface layer, and the diffusion layer is left at 80 ° C. and 85% RH for 1000 hours. Also, the disk characteristics are preserved immediately after film formation. Alternatively, after or immediately before the formation of the first reflective layer,
Oxygen or nitrogen may be intentionally introduced into a vacuum in a film forming apparatus to form an oxide or nitride layer by sputtering as thin as possible. This method is preferable in terms of working steps because it is not necessary to break the vacuum.

In any case, the diffusion preventing layer is usually at most 200 °, preferably at most 100 °, more preferably at most 50 °, so that it does not interfere with the thermal resistance itself. Most preferably, it is about 0.1 to 5 nm. It can be confirmed from the same Auger depth profile that this alone can sufficiently prevent the mutual diffusion of aluminum and silver. The foregoing has described a CD-RW compatible with a low reflectivity but CD compatible, which is an extremely limited and specific application example of the present invention. This is effective for improving the speed dependency and the recording power dependency, and is not particularly limited to this CD-RW. It is considered that the present invention is also effective for a rewritable type high-density digital video disk (so-called DVD) which is currently proposed.

Also, the widening of the linear velocity margin according to the present invention allows the so-called constant angular velocity (CAV).
It is also possible to overcome the problem of the recording characteristic difference caused by the linear velocity difference between the inner and outer circumferences of the disk used at a constant rotation speed such as y) and ZCAV (zoned CAV). Hereinafter, other design elements of the optical recording medium of the present invention will be described with reference to FIG.

The substrate 1 shown in FIG. 1 can be made of resin, glass, or metal. When light is incident from the substrate side, a transparent resin or transparent glass is used, and polycarbonate, acrylic, polyolefin, or transparent glass can be used. Among them, polycarbonate resin is the most preferable because it has the track record of being used most widely in CDs and is inexpensive.

When recording / reproducing is performed without passing through the substrate, opaque resin, glass, or metal can be used. Examples of the resin include acrylic resin, norbornene-based polyolefin resin, liquid crystal polymer, polycarbonate and the like. Examples include polymethyl methacrylate (PMMA), ARTON (Nippon Synthetic Rubber Co., Ltd., hydrogenated norbornene-based ester-substituted cyclic olefin polymer), and ZEONEX (Nippon Zeon Co., Ltd., hydrogenated hydrogenated norbornene-based cyclic olefin polymer) ), Aromatic polyester-based liquid crystal polymers, polycarbonates, and the like.

The lower protective layer 2 is provided to prevent deformation due to high temperature during recording. The material of the lower protective layer 2 is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like. Generally, oxides, sulfides, nitrides, Ca, and M of metals and semiconductors having high transparency and high melting point are used.
g, a fluoride such as Li can be used. Others
Various materials that can be used for the upper protective layer can be used.

These oxides, sulfides, nitrides, and fluorides do not always need to have a stoichiometric composition, and it is effective to control the composition or use a mixture for controlling the refractive index and the like. is there. Considering the repetitive recording characteristics, a dielectric mixture is preferred. More specifically, a mixture of ZnS or a rare-earth sulfide and a heat-resistant compound such as an oxide, a nitride, and a carbide may be used. Like the upper protective layer, the film density of these protective layers is preferably 80% or more of the bulk state from the viewpoint of mechanical strength.

The thickness of the lower protective layer is usually from 10 to 500 nm.
It is. If the thickness of the lower protective layer is too small, the effect of preventing deformation of the substrate or the recording film is insufficient, and the lower protective layer tends not to function as a protective layer. On the other hand, if the thickness is too large, the internal stress of the dielectric itself and the difference in elastic properties with the substrate become remarkable, and cracks tend to occur. In particular, since the lower protective layer has a role of suppressing substrate deformation due to heat, the lower protective layer is
m or more. If it is too thin, microscopic substrate deformation may accumulate during repeated overwriting, and the reproduction light may be scattered, resulting in a significant increase in noise.

The upper limit of the thickness of the lower protective layer is generally substantially 200 nm from the viewpoint of the film formation time, but if it is too thick, the groove shape seen on the recording layer surface may be changed. That is, the groove depth may be smaller than the intended shape on the substrate surface, or the groove width may be smaller than the intended shape on the substrate surface. Therefore, it is more preferably 150 nm or less.

Incidentally, the first reflection layer and diffusion prevention layer mainly composed of aluminum according to the mode (1), and the second reflection layer mainly composed of silver.
The layer configuration of the reflection layer has a light reflection function of high reflectance and a heat radiation function of high thermal conductivity as a whole, and is stable over time. Therefore, even when these are provided on the protective layer containing no sulfur, a very excellent optical information recording medium can be obtained. In particular, the first reflective layer is made of an aluminum alloy containing 0.1 to 2 atomic% of tantalum, the diffusion preventing layer is made of tantalum, and the second reflective layer is made of pure silver. There is little precipitation of tantalum inside, and stable reflectance and thermal conductivity can be obtained for an extremely long period.

In the embodiment (2), the intermediate layer does not form a compound with silver, and has both the solid solubility of the intermediate layer element in silver and the solid solubility of silver in the intermediate layer element. It is composed of an element of 5 atomic% or less, and further, an element whose reactivity with sulfur is low or whose sulfide is chemically stable. Alternatively, the intermediate layer is made of an element that forms a complete solid solution with silver, is a metal or semiconductor oxide, nitride, carbide, or is made of amorphous carbon.

As a result, the temporal change of the recording characteristics can be suppressed only by forming a single intermediate layer. As the material that can be used for the intermediate layer in the mode (2), the same materials as the various materials exemplified as the material for the diffusion preventing layer in the mode (1) can be used. That is, metals, semiconductors, metal oxides,
Various compounds such as metal nitride, metal carbide, semiconductor oxide, semiconductor nitride, semiconductor carbide, and amorphous carbon can be exemplified.

For example, Ta, Ni, Co, Cr, Si,
At least one selected from the group consisting of W and V is included. Among them, Ta and / or Ni are preferred, and Ta is particularly preferred. As the intermediate layer, aluminum or germanium which easily alloys with silver cannot be used as a single layer. In addition, examples of the metal, semiconductor oxide, nitride, or carbide include at least one selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, tantalum oxide, cerium oxide, lanthanum oxide, and yttrium oxide.

Examples of the amorphous carbon that can be used as the diffusion preventing layer include amorphous hydrogenated carbon. Particularly preferred materials are metals or carbon. Tantalum oxide can also serve as both a diffusion prevention layer and a dielectric protection layer. In a phase change recording medium, tantalum oxide is particularly preferable because it is one of the few excellent protective layer materials.

When a material that absorbs laser light, such as Ta or Ni, is used for the intermediate layer, it is optically disadvantageous and the intensity of the recorded signal may be slightly reduced. Therefore, a ZnS-SiO ₂ layer is used as a protective layer,
And productivity, a thin Al alloy layer on ZnS-SiO ₂ in the case of a good Ag economical like used as the reflective layer, an intermediate layer of the present invention, it is effective to provide the Ag layer in this order.

Incidentally, other elements may be added to the intermediate layer as long as its function is not practically impaired. The thickness of the intermediate layer is usually 1 nm or more, preferably 5 nm or more, and usually 100 nm or less, preferably 50 nm.
Or less, particularly preferably 20 nm or less. If the thickness is less than 1 nm, the effect as an intermediate layer is lost, and if it exceeds 100 nm, the effect of the reflection layer as a heat radiation layer tends to be weakened. Further, the substrate may be deformed or cracked by the stress of the film. Production costs and tact are also worse.

Another part of the structure of the optical information recording medium according to the mode (2) will be described. In the mode (2), the basic layer configuration is the same as that in the mode (1). As the substrate, a transparent resin such as polycarbonate, acrylic, or polyolefin, or glass can be used. Among them, polycarbonate, which has a proven track record and is inexpensive, is preferable.

However, in the case of using a floating type head or a contact type head for recording / reproducing while bringing the head close to the medium, resin, glass or metal having higher rigidity and heat resistance of the substrate may be used. When recording / reproduction is not performed through the substrate, the substrate does not need to be transparent. The recording layer is usually covered on the top and bottom with a protective layer.

The material for the protective layer is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like. Generally, oxides, sulfides, nitrides, and fluorides such as Ca, Mg, and Li of metals and semiconductors having high transparency and high melting point can be used. These oxides, sulfides, nitrides, and fluorides do not always need to have a stoichiometric composition, and it is also effective to control the composition for controlling the refractive index and the like, or to use a mixture. Considering the repetitive recording characteristics, a dielectric mixture is preferred. More specifically, Z
A mixture of nS or a rare-earth sulfide and a heat-resistant compound such as an oxide, a nitride or a carbide may be used. For example, ZnS and SiO
The mixture of ₂ is often used for a protective layer of a phase change optical disk.

The upper protective layer provided on the reflective layer side of the recording layer contains sulfur, and preferably contains sulfides such as ZnS, TaS ₂ and rare earth sulfide. In addition, as the material of the upper and lower protective layers, the specific materials exemplified in the embodiment (1) can be used. The film density of these protective layers is 8 in the bulk state.
0% or more is desirable in terms of mechanical strength (Th
in Solid Films, Vol. 278 (1996), 74-8
1 page).

The thickness of the protective layer is usually from 10 to 500 nm. If the thickness is too small, the effect of preventing deformation of the substrate or the recording film is insufficient, and tends not to serve as a protective layer. On the other hand, if it is too thick, the internal stress of the dielectric itself and the difference in elastic properties with the substrate become remarkable, and cracks tend to occur. In particular, the lower protective layer needs to suppress substrate deformation due to heat, and is usually 50 nm or more. If the thickness is too thin, microscopic substrate deformation may be accumulated during repeated overwriting, and the reproduction light may be scattered to significantly increase noise.

The upper limit of the thickness of the lower protective layer is generally substantially 200 nm from the viewpoint of the film forming time, but if it is too thick, the groove shape seen on the recording layer surface may be changed. That is, the groove depth may be smaller than the intended shape on the substrate surface, or the groove width may be smaller than the intended shape on the substrate surface. Therefore, it is more preferably 150 nm or less.

On the other hand, the thickness of the upper protective layer is usually 5 nm or more, preferably 10 nm or more, for suppressing deformation of the recording layer. On the other hand, if the thickness is too large, microscopic plastic deformation tends to accumulate during repeated overwriting inside the upper protective layer, which again scatters reproduction light and increases noise. The upper limit is usually 60 nm, preferably 50 nm.
It is.

As the recording layer, a known phase change type optical recording layer can be used. For example, GeSbTe, InSbTe, AgS
Compounds such as bTe and AgInSbTe are selected as overwritable materials. Above all, ｛(Sb _{2
Te 3) 1-x (GeTe} ) x} 1-y Sb y alloy (0.2 <x
<0.9, 0 ≦ y <0.1) or Ma _w (Sb _z Te)
_1-z ) _1-w alloy (however, 0 ≦ w ≦ 0.3, 0.5 ≦ z ≦
0.9, Ma is In, Ga, Zn, Ge, Sn, Si,
Cu, Au, Ag, Pd, Pt, Pb, Cr, Co,
O, N, S, Se, Ta, Nb, V, Bi, Zr, T
The thin film mainly containing i, Mn, Mo, Rh and at least one selected from the group consisting of rare earth elements) is stable in both crystalline and amorphous states, and is capable of high-speed phase transition between the two states.

Further, there is an advantage that segregation hardly occurs when repeated overwriting is performed, and this is the most practical material. When the recording layer is of a phase change type, its thickness is usually 10 nm or more and 100 nm or less. If the thickness of the recording layer is too thin, it is difficult to obtain a sufficient contrast, and the crystallization speed tends to be slow, so that it is difficult to erase the recording in a short time.

On the other hand, if the thickness is too large, it is still difficult to obtain optical contrast, and cracks are likely to occur. And especially preferably, it is 10 nm or more and 30 nm or less. If it is less than 10 nm, the reflectance is too low, and
If the thickness is larger than nm, the heat capacity tends to increase, and the recording sensitivity tends to deteriorate.

The recording layer is often obtained by sputtering an alloy target in an inert gas, particularly an Ar gas. Incidentally, the thickness of the recording layer and the protective layer, in addition to the above mechanical strength, from the viewpoint of reliability, taking into account the optical interference effect associated with the multilayer structure, good laser light absorption efficiency,
The amplitude of the recording signal, that is, the contrast between the recorded state and the unrecorded state is selected so as to increase.

As described above, the recording layer, the protective layer, and the reflective layer are formed by a sputtering method or the like. It is desirable to form a film using an in-line apparatus in which a target for a recording film, a target for a protective film, and if necessary, a target for a reflective layer material are installed in the same vacuum chamber, from the viewpoint of preventing oxidation and contamination between layers. It is also excellent in productivity.

The material containing silver as the main component used for the reflection layer in the mode (2) can be the same as the material containing silver as the main component used for the second reflection layer in the mode (1). The thickness is usually 30 to 300 nm, preferably 40 to 200 nm. If it is too thick, the heat capacity of the reflective layer itself will be too large and the recording sensitivity will decrease,
In addition, cracks are easily generated. If it is too thin, light will be transmitted, and sufficient reflectance cannot be obtained. Further, the heat dissipation effect inherent in the silver reflection layer cannot be obtained.

[0127]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.
The solid solubility of each element is “Constitution of Binary Alloys”,
(Max Hansen and KurtAnderko, second edition (1985),
Genium Publishing Corporation, New York).

The composition of each layer was determined by X-ray fluorescence analysis, atomic absorption analysis,
It was confirmed by combining X-ray excitation photoelectron spectroscopy and the like. The density of the protective layer film was determined from the change in weight when the film was formed to be as thick as several hundred nm on the substrate. The film thickness was used by calibrating the fluorescent X-ray intensity with the film thickness measured by a stylus meter. The sheet resistivity of the reflective layer was measured with a four-probe resistance meter (Loresta FP manufactured by Mitsubishi Yuka (currently Dia Instruments)). The resistance was measured on a reflective layer formed on a glass or polycarbonate resin substrate serving as an insulator, or on the reflective layer serving as the uppermost layer after forming the four-layer structure (before the UV-curable resin protective coat) shown in FIG. .

Since the upper protective layer is a dielectric thin film and made of an insulator, there is no influence on the measurement of the sheet resistivity. In addition, the measurement is performed with a disk substrate shape having a diameter of 120 mm, which can be regarded as a substantially infinite area. The obtained resistance value R was applied to the following equation, and the sheet resistivity rS and the volume resistivity rV were calculated. Here, t is the film thickness, and F is a correction coefficient determined by the shape of the thin film region to be measured, and takes a value of 4.3 to 4.5. Here, it is set to 4.4.

RS = F · R (2) rV = rS · t (3) The disk characteristics were evaluated under the following conditions unless otherwise specified. For recording / reproducing evaluation, a DDU1000 evaluator manufactured by Pulstec was used, and the recording linear velocity was changed from 1.2 m / s to 4.8 m / s.
The playback speed was twice as fast as that of a CD (2.4 m / s). The wavelength of the optical head is 780 nm, and the NA is 0.55.

Using the pulse strategy shown in FIG. 2, an EFM (Eight-Fourteen modulation) random pattern was recorded. The recording mark forming unit irradiates the recording power Pw alternately with the recording power Pw in the recording pulse interval and the bias power Pb in the off pulse interval, and applies the erasing power Pe to the interval between the marks. However, there is a case where Pb = Pe in the off-pulse section at the end of the mark at a linear velocity of 2.8 m / s or more. Pb was constant at 0.8 mW at all linear velocities.

The clock cycle at twice the speed (2.4 m / s) of CD is 115 nsec, and the clock cycle T is made inversely proportional to the linear velocity when switching the linear velocity. Since the reproduction speed is twice as fast, the allowable value of the jitter is 17.5n in the CD standard.
sec. The recording layer immediately after film formation is amorphous, and has a wavelength of 830 nm focused on a major axis of about 70 μm and a minor axis of about 1.3 μm.
An initializing power of 500 to 600 mW was applied at a linear velocity of 3.5 m / s with a laser light beam of m to crystallize the entire surface to obtain an initial (unrecorded) state.

At this power, it is considered that the recording layer is crystallized once when it is melted and re-solidified. The substrate is a polycarbonate substrate having a thickness of 1.2 mm, and unless otherwise specified, a pitch of 1.6 μm and a width of 0.53 μm by injection molding.
A groove having a depth of m and a depth of 32 nm is formed. Recording was made in this groove.

The groove shape was measured using an optical diffraction method similar to a U groove. Of course, the groove shape may be measured with a scanning electron microscope or a scanning probe microscope. in this case,
The groove width at half the groove depth is used. Example 1 A lower protective layer (ZnS) ₈₀ (Si
O ₂ ) ₂₀ at 95 nm, Ag ₅ In ₅ Sb _61.5 Te _28.5 recording layer at 17.5 nm, upper protective layer (ZnS) ₈₀ (Si
An O ₂ ) ₂₀ film was formed to a thickness of 38 nm, an Al ₉₉ Ta ₁ alloy having a thickness of 40 nm was formed as the first reflection layer, and a 60 nm-thick Ag film was formed as the second reflection layer. From the lower protective layer to the first reflective layer, it is created by sputtering without releasing the vacuum,
After forming the first reflective layer, the film was opened to the atmosphere and allowed to stand for 5 hours, and then the second reflective layer was formed again by sputtering in a vacuum.

After the formation of the second reflective layer, an ultraviolet-curable resin was laminated as an overcoat layer by 4 μm by spin coating. The first reflective layer was formed at an ultimate vacuum of 2 × 10 ⁻⁴ Pa or less, an Ar pressure of 0.54 Pa, and a film formation rate of 1.3 nm / sec. The volume resistivity was 92 nΩ · m. Impurities such as oxygen and nitrogen were less than the detection sensitivity in X-ray excitation photoelectron spectroscopy, and were considered to be less than about 1 atomic% in total.

The deposition of the second reflective layer is performed at an ultimate vacuum of 2 × 10 ^−4.
Pa or less, Ar pressure 0.54 Pa, film formation rate 1.3 nm
/ Sec. The volume resistivity was 32 nΩ · m. Impurities such as oxygen and nitrogen were less than the detection sensitivity in X-ray excitation photoelectron spectroscopy, and were considered to be less than about 1 atomic% in total. (ZnS) ₈₀ (SiO ₂ ) _{20 The} protective layer has a film density of 3.
Was 94% of the theoretical bulk density of 3.72 g / cm ³ at 50 g / cm ^3.

This medium was set to Pe / Pw = 0.5 using the pulse strategy shown in FIG.
s) The recording power dependence of 3T mark jitter and 3T space jitter when recording was performed is shown as an initial value in FIG. Similarly, FIG. 5 shows, as initial values, the recording power dependency when quadruple speed (4.8 m / s) recording is performed with Pe / Pw = 0.5 by halving the clock cycle by the pulse strategy of FIG. Was. In this case, the last off-pulse section was set to 0.

In each case, measurement was performed at double speed (2.4 m / s) after overwriting 10 times under predetermined conditions. 4 and 5 that the 3T mark jitter and the 3T space jitter have wide power margins at 2 × speed and 4 × speed. This disc is heated at 80 ° C, 8
After being left for 500 hours in a high-temperature and high-humidity environment of 0% RH, the 2 × -speed and 4 × -speed recording portions were reproduced. As shown in FIG. 4 and FIG. No deterioration was observed in the jitter.

As described above, wide linear velocities and recording power margins were obtained at 2 to 4 times speed. Also, repeated overwriting was possible up to about 5000 times. Also,
The block error rate in the CD standard of the disc before the accelerated test is an average of 10 / sec, and a maximum of 30 / sec.
There was almost no increase after the 00-hour accelerated test.

When this disk was analyzed by Auger depth profile, it was found that there was a peak indicating the presence of oxygen at the interface between the first reflective layer and the second reflective layer, and that an Ag or Al oxide layer was formed at the interface. It was confirmed. Comparative Example 1 The layer configuration and the film forming conditions were exactly the same as in Example 1. However, all the thin films from the lower protective layer to the second reflective layer were formed by sputtering without releasing the vacuum.

The conditions for forming the first reflective layer and the second reflective layer were the same as those in Example 1, and showed the same volume resistivity. At 2 × speed and 4 × speed, a wide power margin was measured for both 3T mark jitter and 3T space jitter. Also, repeated overwriting was possible up to about 5000 times.

However, when the film was left standing for 50 hours under the conditions of high temperature and high humidity of 80 ° C. and 85% RH after the film was formed, the jitter was greatly deteriorated. In addition, the average block error rate increased to 100 / sec or more. An attempt was made to perform double speed recording on this disk, but no amorphous mark was formed at all. When this disk was visually observed from the reflective layer side, the surface was seen to be silver immediately after the film formation,
After the 500-hour accelerated test, it was slightly bluish and deteriorated. When an Auger depth profile was measured for this, it was found that the first reflective layer made of Al alloy and the second reflective layer made of Ag were completely alloyed by mutual diffusion. That is, it is considered that the reflective layer was alloyed and the thermal conductivity was lowered, so that recording could not be performed.

The solid solubility of Al with Ag was 42 at%.
Met. Comparative Example 2 A lower protective layer (ZnS) ₈₀ (S
iO ₂ ) ₂₀ at 95 nm, Ag ₅ In ₅ Sb _61.5 Te _28.5 recording layer at 17.5 nm, upper protective layer (ZnS) ₈₀ (SiO
₂ ) A film of ₂₀ was formed to a thickness of 38 nm and a reflective layer Ag was formed to a thickness of 50 nm.

All the thin films were formed by the sputtering method up to the reflection layer without releasing the vacuum. After forming the reflective layer, 4 μm of UV curable resin is used as an overcoat layer by spin coating.
m. The deposition of the reflective layer is performed at an ultimate vacuum of 2 × 10 ⁻⁴ Pa
Hereinafter, an Ar pressure of 0.54 Pa and a film formation rate of 1.3 nm / sec were used. Its volume resistivity was 32 nΩ · m. Impurities such as oxygen and nitrogen were less than the detection sensitivity in X-ray excitation photoelectron spectroscopy, and were considered to be less than about 1 atomic% in total.

The (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer had a film density of 3.50 g / cm ³ and a theoretical bulk density of 3.72 g.
/ Cm ³ was 94%. When this disk was evaluated, it was found that the 3T mark jitter and the 3T space jitter both had wide power margins at 2 × speed and 4 × speed. However, repeated overwriting is 1000
Only about once.

When this disk was visually observed from the reflective layer side, the surface appeared silver immediately after the film formation, but the color changed after the 500-hour acceleration test. It is considered that Ag reacted with sulfide sulfur in the upper protective layer.
Similar discoloration of the Ag film was observed in the medium left at room temperature for several days after the film formation. Example 2 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer _{(105nm), Ag 5 In 5} Sb 62 Te 28 recording layer _{(17nm), (ZnS) 80} (SiO 2) 2 0 upper protective layer (40nm), Ta ₂ O ₅ interlayer (10 nm), Ag
The structure of the reflection layer (90 nm) is created by a sputtering method,
On top of this, a protective coat made of an ultraviolet curable resin was further applied. After initial crystallization of this disk, recording was performed by forming an amorphous mark in the groove.

Double speed recording was performed on this medium using the pulse strategy shown in FIG. 2 at Pe / Pw = 0.5 and a recording power of 10 mW. After that, this disc is
After keeping the environment at 80 ° C. and 80% RH for 500 hours, the same recording was performed again. (Hereinafter, an operation of maintaining the environment at 80 ° C. and 80% RH for 500 hours is referred to as an acceleration test.) The 3T space jitter in the recording before and after the acceleration test was 12.5, respectively.
The degradation was small at nsec and 14.3 nsec. The results were almost the same for discs in which the thickness of the intermediate layer (tantalum oxide layer) was changed from 10 to 50 nm so as not to change the total thickness of the upper protective layer and the intermediate layer. The signal intensity was sufficiently large and almost no deterioration was observed.

Example 3 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₅ Sb ₆₂ Te ₂₈ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Ta intermediate layer (40 nm), Ag reflective layer (70 nm) Was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon.
When the same recording and evaluation as in Example 2 were performed, the 3T space jitter was 15.0 ns each before and after the acceleration test.
The deterioration was small at ec of 17.4 nsec. The results were almost the same for disks in which the thickness of the intermediate layer (Ta layer) was changed from 10 to 40 nm. The signal intensity was smaller than that of Example 2, but at a level that was no problem.

The solid solubility of Ta with Ag is considered to be 0 at%. Example 4 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₅ Sb ₆₂ Te ₂₈ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Ni intermediate layer (40 nm), Ag reflective layer (70 nm) Was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon.
When the same recording and evaluation as in Example 2 were performed, the 3T space jitter was 15.0 ns each before and after the acceleration test.
ec, 15.0 nsec, the deterioration was small. The results were almost the same for the disk in which the thickness of the intermediate layer (Ni layer) was changed from 10 to 40 nm. The signal intensity was smaller than that of Example 2, but at a level that was no problem.

It is considered that the solid solubility of Ni in Ag is 0 at% and the solid solubility of Ag in Ni is 2 at% or less. Comparative Example 3 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Create lower protective layer _{(95nm), Ag 5 In 5} Sb 62 Te 28 recording layer (18 nm), a structure of _{(ZnS) 80 (SiO 2)} 20 upper protective layer (40 nm), Ag reflective layer (70 nm) by sputtering Then, a protective coat made of an ultraviolet curable resin was further applied thereon. When the same environmental resistance test as in Example 2 was performed, a number of defects observable by microscopic observation from the Ag side appeared. Furthermore, when recording was repeated on the disk before the accelerated test, the recording characteristics deteriorated after about 100 times. Oops.

Comparative Example 4 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₅ Sb ₆₂ Te ₂₈ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Al alloy reflective layer (40 nm), Ag reflective layer (70 nm) ) Was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon. When recording and evaluation were performed in the same manner as in Example 2, after the acceleration test, the recording mark was not written and deteriorated to the point where measurement was impossible. When the disk after the acceleration test was analyzed by Auger electron spectroscopy, it was confirmed that Al and Ag were interdiffused.

Comparative Example 5 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer _{(105nm), Ag 5 In 5} Sb 62 Te 28 recording layer _{(17nm), (ZnS) 80} (SiO 2) 2 0 upper protective layer (50nm), Al ₉₉ Ta ₁ alloy reflective layer (220n
The structure of m) was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon. Example 2
When the same recording and evaluation were performed as in the above, the 3T space jitter was 11.7 nsec and 3T respectively before and after the acceleration test.
The deterioration was large at 0.1 nsec.

Comparative Example 6 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₅ Sb ₆₂ Te ₂₈ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Ti layer (40 nm), Ag reflective layer (7
0 nm) was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon. When recording and evaluation were performed in the same manner as in Example 2, after the acceleration test, the recording mark was not written and deteriorated to the point where measurement was impossible. It is considered that Ti and Ag mutually diffused and alloyed.

The solid solubility of Ti with Ag was about 5 at% at the eutectic point of 850 ° C. However,
Ti and Ag form the compound TiAg. Comparative Example 7 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₅ Sb ₆₂ Te ₂₈ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Zr layer (40 nm), Ag reflective layer (7
0 nm) was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon. When the same accelerated test as in Example 2 was performed, a number of visually observable defects appeared.

Although Zr and Ag do not form a solid solution, Zr is composed of Ag and the compound ZrAg, probably Zr _2.
Ag and Zr ₃ Ag are formed. Comparative Example 8 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₆ Sb ₆₃ Te ₂₆ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Ge layer (40 nm), Ag reflective layer (7
0 nm) was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon. When an acceleration test similar to that in Example 2 was performed, it was found that the color of the reflective film was white silver before the test, but it was discolored with the same color as red. Under normal recording conditions at 2 × speed, no amorphous mark could be recorded at all. When the signal was recorded at a quadruple speed linear velocity with a pulse shorter than usual, an amorphous mark could be recorded.

The solid solubility of Ge in Ag is eutectic point 65
It was about 9 at% at 1 ° C. Example 5 A lower protective layer (ZnS) ₈₀ (SiO ₂ ) ₂₀ of 205 nm, Ag ₅ In ₆
18 nm Sb ₆₃ Te ₂₆ recording layer, upper protective layer (ZnS)
_{A 20} nm film of ₈₀ (SiO ₂ ) ₂₀ was formed, and a 40 nm thick Al _99.5 Ta _0.5 alloy was formed as the first reflective layer, and a 70 nm thick Ag film was formed as the second reflective layer.

From the lower protective layer to the first reflective layer, the first reflective layer was formed by a sputtering method without releasing the vacuum. A reflective layer was formed. After the formation of the second reflective layer, an ultraviolet curable resin was laminated as an overcoat layer by 4 μm by spin coating. Two of the resulting disks were bonded together so that the overcoat layers faced each other.

The first reflective layer was formed at an ultimate vacuum of 4 × 10 ^−4.
The test was performed at an Ar pressure of 0.55 Pa or less under Pa. The volume resistivity was 55 nΩ · m. Impurities such as oxygen and nitrogen are below the detection sensitivity in X-ray excitation photoelectron spectroscopy,
It was considered to be less than atomic%. The second reflective layer was formed at an ultimate vacuum of 4 × 10 ⁻⁴ Pa or less and an Ar pressure of 0.35 Pa. The volume resistivity was 32 nΩ · m. Impurities such as oxygen and nitrogen were less than the detection sensitivity in X-ray excitation photoelectron spectroscopy, and were considered to be less than about 1 atomic% in total.

In this medium, a light source wavelength of 635 nm, NA
Using an evaluator of 0.60, a linear velocity of 3.5 m / s, 8-16 modulation, 0.266 um / bit (3T = 0.4 u
m), Pe / Pw using the pulse strategy shown in FIG.
= 0.5, the Pw dependence of the jitter, the reflectance, and the modulation when performing double speed recording is shown in FIG.
e0).

A linear velocity of 3.5 was obtained by using a pulse strategy obtained by slightly changing the pulse strategy shown in FIG.
When recording was performed at a recording power of 13 mW at m / s, the jitter was 10% or less. 80 ℃
After leaving under high temperature and high humidity of 80% RH for 100 hours, recording was similarly performed at 7 m / s.
0h), no deterioration was observed.

Example 6 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₆ Sb ₆₂ Te ₂₇ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Al _99.5 Ta _0.5 alloy first reflective layer (4
0 nm), a Ta intermediate layer (40 nm), and a Ag second reflective layer (80 nm) were formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon.
The Pw dependency of the jitter, the reflectance and the degree of modulation in the same recording and evaluation as in Example 1 is shown as an initial value (Time 0) in FIGS.

After this disk was left under high temperature and high humidity of 80 ° C. and 80% RH for 100 hours, the same recording was performed, and no deterioration was observed as shown in FIGS. 8 and 9 (Time 100h). . The solid solubility of Ta with Ag is considered to be 0 at%. Example 7 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₆ Sb ₆₃ Te ₂₆ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ upper protective layer (40 nm), amorphous carbon intermediate layer (40 nm),
The structure of the Ag reflection layer (70 nm) was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon. When the same recording and evaluation were performed as in Example 2,
No change was observed in the 3T space jitter between the recordings before and after the acceleration test.

The solid solubility of C with Ag was 0 at%. Example 8 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₆ Sb ₆₃ Te ₂₆ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Co intermediate layer (40 nm), Ag reflective layer (70 nm) Was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon.
When the same recording and evaluation as in Example 2 were performed, no change was observed in the 3T space jitter in the recording before and after the acceleration test.

The solid solubility of Co with Ag was 0 at%. Example 9 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₆ Sb ₆₃ Te ₂₆ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Cr intermediate layer (40 nm), Ag reflective layer (70 nm) Was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon.
The same recording and evaluation as in Example 2 showed no change in 3T space jitter between before and after the acceleration test.

The solid solubility of Cr with Ag was 0 at%. Example 10 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₆ Sb ₆₃ Te ₂₆ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Si intermediate layer (40 nm), Ag reflective layer (70 nm) Was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon.
No alloying of the reflective film was observed after the accelerated test, and recording and evaluation were performed in the same manner as in Example 2. As a result, a change was observed in the reflectance, but recording was possible.

The solid solubility of Si with Ag was 0 at%. Example 11 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₆ Sb ₆₃ Te ₂₆ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), W intermediate layer (40 nm), Ag reflective layer (70 nm) Was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon.
No alloying of the reflective film was observed after the accelerated test.

The solid solubility of W with Ag was 0 at%. Example 12 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₆ Sb ₆₃ Te ₂₆ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), V intermediate layer (40 nm), Ag reflective layer (70 nm) Was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon.
No alloying of the reflective film was observed after the accelerated test.

The solid solubility of V with Ag is considered to be 0 at%. Example 13 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₆ Sb ₆₃ Te ₂₆ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Au intermediate layer (40 nm), Ag reflective layer (70 nm) Was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon.
Although alloying of the reflective film was observed after the acceleration test, the same recording and evaluation as in Example 2 showed no change in 3T space jitter between the recordings before and after the acceleration test.

After the accelerated test, Au and Ag may have formed a solid solution. However, since Au and Ag form a complete solid solution, phase separation that greatly changes the reflectance and the thermal conductivity occurs. Probably not. Example 14 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Lower protective layer (95 nm), Ag ₅ In ₆ Sb ₆₃ Te ₂₆ recording layer (18 nm), (ZnS) ₈₀ (SiO ₂ ) ₂₀ Upper protective layer (40 nm), Pd intermediate layer (40 nm), Ag reflective layer (70 nm) Was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon.
Although alloying of the reflective film was observed after the acceleration test, the same recording and evaluation as in Example 2 showed no change in 3T space jitter between the recordings before and after the acceleration test.

After the accelerated test, Pd and Ag may have formed a solid solution. However, since Pd and Ag form a complete solid solution, phase separation that greatly changes the reflectance and the thermal conductivity occurs. Probably not.

[0171]

According to the present invention, an optical information recording medium having good disk characteristics over a wide range of linear speeds and a wide range of powers and having excellent storage stability can be obtained. Also, by using the optical head and the medium, it is possible to obtain a compact, high-density, high-speed recording / reproducing information recording apparatus. A recording device can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an example of an optical information recording medium according to the present invention.

FIG. 2 is a diagram illustrating an example of a recording pulse strategy used in the present invention.

FIG. 3 is an explanatory diagram illustrating a state of thermal diffusion of a recording layer.

FIG. 4 is a graph showing the recording power dependence of jitter at 2.4 m / s in Example 1.

FIG. 5 is a graph showing the recording power dependence of jitter at 4.8 m / s in Example 1.

FIG. 6 is an explanatory diagram of another example of the recording pulse strategy used in the present invention.

FIG. 7 is a graph showing the recording power dependence of the jitter, the reflectance, and the degree of modulation in Example 5.

FIG. 8 is a graph showing recording power dependence of jitter in Example 6.

FIG. 9 is a graph showing the recording power dependence of the reflectance and the degree of modulation in Example 6.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower protective layer 3 Phase change type recording layer 4 Upper protective layer 5 1st reflective layer 6 Diffusion prevention layer 7 2nd protective layer 8 Protective coat layer 9 Reflective layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B41M 5/26 G11B 7/00 626Z G11B 7/00 626 11/10 521F 11/10 521 B41M 5/26 X

Claims (34)

[Claims] 1. A substrate comprising: a substrate; a recording layer; a protective layer containing a sulfur atom; an intermediate layer in contact with the protective layer; and a reflective layer in contact with the intermediate layer and containing silver as a main component. Does not form a compound with silver on the side in contact with the reflective layer, and both the solid solubility of the intermediate layer element in silver and the solid solubility of silver in the intermediate layer element are 5 atomic%. An optical information recording medium comprising the following elements, wherein the side in contact with the protective layer has low reactivity with sulfur or an element whose sulfide is chemically stable. 2. The silver content in the reflective layer is 95 atomic%.
The optical information recording medium according to claim 1, which is as described above. 3. The reflective layer is made of Ti, V, Ta, Nb, W,
Co, Cr, Si, Ge, Sn, Sc, Hf, Pd, R
The optical element according to claim 2, comprising pure silver or a silver alloy containing at least one element selected from the group consisting of h, Au, Pt, Mg, Zr, Mo, and Mn in an amount of 0.2 atomic% or more and 2 atomic% or less. Information recording medium. 4. The optical information recording medium according to claim 1, wherein the protective layer contains a sulfide. 5. A recording layer comprising a Ma _w (Sb _z Te _1-z ) _1-w alloy thin film (where 0 ≦ w ≦ 0.3, 0.5 ≦ z ≦ 0.
9, Ma is In, Ga, Zn, Ge, Sn, Si, C
u, Au, Ag, Pd, Pt, Pb, Cr, Co, O,
N, S, Se, Ta, Nb, V, Bi, Zr, Ti, M
The optical information recording medium according to any one of claims 1 to 4, wherein the medium comprises at least one selected from n, Mo, Rh and a rare earth element. 6. The optical information recording medium according to claim 5, wherein 0 ≦ w ≦ 0.2. 7. The method according to claim 5, wherein 0.6 ≦ z ≦.
0.8 for an optical information recording medium. 8. The optical element according to claim 1, wherein the intermediate layer is made of an element having a eutectic temperature of 500 ° C. or more in a binary alloy phase diagram with silver on the side in contact with the reflective layer. Information recording medium. 9. The optical information recording medium according to claim 8, wherein the intermediate layer is made of at least one selected from the group consisting of tantalum, nickel, cobalt, chromium, silicon, tungsten and vanadium on the side in contact with the reflective layer. 10. The optical information recording medium according to claim 9, wherein the intermediate layer is made of at least one selected from the group consisting of tantalum and nickel on the side in contact with the reflective layer. 11. The intermediate layer, on the side in contact with the protective layer, does not form a compound with sulfur in a binary alloy phase diagram with sulfur or the compound with sulfur decomposes, sublimes, melts, and reacts at 500 ° C. or lower. 11. The optical information recording medium according to claim 1, comprising an element that does not cause transformation. 12. The intermediate layer is made of at least one selected from the group consisting of aluminum, silicon, germanium, tantalum, nickel, cobalt, chromium, tungsten and vanadium on the side in contact with the protective layer.
2. The optical information recording medium according to 1. 13. The optical information recording medium according to claim 12, wherein the intermediate layer is formed of at least one selected from aluminum, silicon, germanium, tantalum and nickel on a side in contact with the protective layer. 14. The optical information recording medium according to claim 12, wherein the intermediate layer is made of at least one selected from aluminum, tantalum and nickel on the side in contact with the protective layer. 15. An intermediate layer comprising at least two layers of a layer mainly composed of aluminum provided in contact with a protective layer and a layer provided in contact with a reflective layer for preventing diffusion of aluminum and silver. The optical information recording medium according to claim 1. 16. The optical information recording medium according to claim 15, wherein the layer for preventing the diffusion of aluminum and silver is a compound of aluminum or silver and oxygen and / or nitrogen. 17. The optical information recording medium according to claim 16, wherein the layer for preventing diffusion of aluminum and silver is a compound of aluminum or silver and oxygen. 18. The optical information recording medium according to claim 15, wherein the layer for preventing diffusion of aluminum and silver contains tantalum or nickel as a main component. 19. The optical information recording medium according to claim 15, wherein the content of aluminum in the layer containing aluminum as a main component is 95 atomic% or more. 20. A layer mainly composed of aluminum,
a, Ti, Co, Cr, Si, Sc, Hf, Pd, P
20. The optical information recording device according to claim 19, comprising an aluminum alloy containing at least one element selected from the group consisting of t, Mg, Zr, Mo, and Mn in an amount of 0.2 atomic% or more and 2 atomic% or less, or pure aluminum. Medium. 21. The optical information recording medium according to claim 1, wherein the intermediate layer is made of at least one selected from tantalum, nickel, cobalt, chromium, silicon, tungsten, and vanadium. 22. A medium for recording, reproducing and erasing an amorphous mark whose mark length has been modulated by irradiating a focused light beam, wherein the substrate, a lower protective layer, and a film thickness are 10 nm or more and 30 nm or more. The following Ma _w (Sb _z Te _1-z ) _1-w alloy thin film (where 0 ≦ w ≦ 0.2, 0.6 ≦ z ≦ 0.8, Ma is I
n, Ga, Zn, Ge, Sn, Si, Cu, Au, A
g, Pd, Pt, Pb, Cr, Co, O, N, S, S
e, Ta, Nb, V, Bi, Zr, Ti, Mn, Mo,
A phase change recording layer made of at least one selected from Rh and a rare earth element), an upper protective layer having a thickness of 30 nm or more and 60 nm or less, a first reflective layer mainly composed of aluminum having a thickness of 5 nm or more and 50 nm or less, 1 A diffusion preventing layer in contact with the reflection layer, and a film thickness of 40 nm or more in contact with the diffusion preventing layer and 20
Volume resistivity of 20 nΩ · m or more and 80 nΩ ·
a second reflective layer containing silver of m or less as a main component, and an optical information recording medium. 23. The volume resistivity of the first reflection layer is 20 nΩ ·
23. The optical information recording medium according to claim 22, which has a value of not less than m and not more than 150 nΩ · m. 24. A substrate comprising: a substrate; a recording layer; a protective layer containing a sulfur atom; an intermediate layer in contact with the protective layer; and a reflective layer in contact with the intermediate layer and containing silver as a main component. Is an optical information recording medium comprising an element forming a complete solid solution with silver. 25. A substrate comprising: a recording layer; a protective layer containing a sulfur atom; an intermediate layer in contact with the protective layer; and a reflective layer in contact with the intermediate layer and containing silver as a main component. Is an optical information recording medium comprising a metal or semiconductor oxide, nitride or carbide, or amorphous carbon. 26. A substrate comprising at least a recording layer, a dielectric protective layer, an intermediate layer, and a reflective layer in contact with the intermediate layer and containing silver as a main component, wherein the intermediate layer is selected from the group consisting of tantalum oxide, tantalum, and nickel. An optical information recording medium comprising at least one of the following. 27. A dielectric protective layer comprising ZnS—SiO ₂ as a main component, an intermediate layer comprising tantalum oxide,
27. The optical information recording medium according to claim 26, wherein the reflection layer contains silver as a main component. 28. The method according to claim 26, wherein the intermediate layer comprises at least a layer mainly composed of aluminum in contact with the dielectric protective layer and a layer made of tantalum or nickel in contact with the reflective layer mainly composed of silver. The optical information recording medium according to the above. 29. An intermediate layer comprising a layer made of an aluminum alloy containing 0.1 to 2 atomic% of tantalum having a thickness of 5 to 50 nm and a layer of tantalum having a thickness of 5 to 50 nm, and a reflective layer 28. The optical information recording medium according to claim 26, wherein the thickness of the optical information recording medium is 30 nm or more and 200 nm or less. 30. The optical information recording medium according to claim 26, wherein the content of silver in the reflective layer is 95 atomic% or more. 31. The reflecting layer is made of Ti, V, Ta, Nb,
W, Co, Cr, Si, Ge, Sn, Sc, Hf, P
31. The silver alloy according to claim 30, comprising pure silver or a silver alloy containing at least one element selected from the group consisting of d, Rh, Au, Pt, Mg, Zr, Mo, and Mn in an amount of 0.2 at% or more and 2 at% or less. Optical information recording medium. 32. A recording layer comprising: Ma _w (Sb _z Te _1-z ) _1-w
Alloy thin film (however, 0 ≦ w ≦ 0.3, 0.5 ≦ z ≦ 0.
9, Ma is In, Ga, Zn, Ge, Sn, Si, C
u, Au, Ag, Pd, Pt, Pb, Cr, Co, O,
N, S, Se, Ta, Nb, V, Bi, Zr, Ti, M
32. The optical information recording medium according to claim 26, wherein the medium comprises at least one selected from n, Mo, Rh and a rare earth element. 33. An information recording apparatus comprising the optical information recording medium according to claim 1 and an optical head. 34. The information recording apparatus according to claim 33, wherein the optical head is one of a floating head and a contact head.