JPH11250500A - Optical recording medium and protective film for optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve repetitive recording and erasing characteristics of an optical recording medium. SOLUTION: The first protective film 3 of the optical recording medium 1 successively laminated with a substrate 2, the first protective film 3, a recording film 4, a second protective film 5 and a reflection film 6 is formed by incorporating nitrogen into a film mixture composed of ZnS and SiO2 and is so formed that the nitrogen density is higher on the recording film 4 side than on the substrate 2 side. The second protective film 5 is formed of a film mixture composed of ZnS and SiO2 . As a result, the recording medium having the improved repetitive characteristic is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium having a recording film made of a phase change type recording material and a protective film for the optical recording medium suitable for the optical recording medium.

[0002]

2. Description of the Related Art In recent years, an optical recording medium capable of high-density recording and capable of erasing and rewriting recorded information has attracted attention. Among the rewritable optical recording media, the phase-change optical recording medium changes the crystal state of the recording film by irradiating a laser beam, and detects a change in the reflectance of the recording film due to such a state change. Things.

As a material of a recording film of a phase change type optical recording medium, a Ge-Te type material having a large difference in reflectance between a crystalline state and an amorphous state and a relatively high amorphous state stability. Is often used. Typical examples of the material include Ge-Te and Ge-T as disclosed in U.S. Patent No. 3,530,441.
e-Sb-S, Ge-Te-S, Ge-Se-S, Ge-Se-Sb, Ge-As-Se, In
So-called chalcogen-based alloy materials such as -Te, Se-Te and Se-As.

In order to improve the stability and the high-speed crystallization, Au (Japanese Patent Application Laid-Open No. 61-219692), Sn and Au
(JP-A-61-270190), Pd (JP-A-62-19490), etc., and the composition of Ge-Te-Se-Sb for the purpose of improving the recording / erasing repetition performance A material having a specified ratio (JP-A-62-73438) has also been proposed. However, none of the above-mentioned compositions can satisfy all of the various properties required for a recording film of a phase-change rewritable optical recording medium. In particular, recording sensitivity,
Improvements in erasing sensitivity, prevention of erasing ratio reduction due to unerased portions during overwriting, and prolonged life of repeated recording / erasing characteristics are the most important issues.

[0005] In contrast, recently, the the use of chemical periodic table Ib-IIIb-VIb ₂ or IIb-IVb-Vb compound called chalcopyrite represented by ₂ is proposed to be applied to the recording film material I have. It is known that among the chalcopyrite-type compounds, AgInTe ₂ can be used as a good recording film material for an optical recording medium by diluting with Sb or Bi (JP-A-3-240590, JP-A-3-240590). JP-A-3-99884, JP-A-3-82593, JP-A-3-73384, etc.). Further, in addition to this, Japanese Patent Application Laid-Open No. 4-267192 and
JP-A-232779 and JP-A-6-166268 disclose a phase-change optical recording medium in which an AgSbTe ₂ phase is generated when a recording film is crystallized.

However, optical recording media using these chalcopyrite-based recording film materials are certainly excellent in C
/ N, erasing ratio, modulation degree, and recording sensitivity, but there is a problem that the life of repeated recording and erasing is only about 1,000 times. In order to solve this problem, the present inventors have developed an Au-In-Sb-Te recording film material having a specific composition, and filed the same prior application (Japanese Patent Application No. 9-46225, Japanese Patent Application No. -210745, Japanese Patent Application No. 9-285785, etc.). This recording film material has excellent C / N,
It has an erasing ratio, modulation degree, recording sensitivity, and repeated recording / erasing characteristics. In particular, the life of the repetitive recording / erasing characteristics is 10,000 times at a linear velocity of 1 to 3 m / s and 100,000 times at a linear velocity of 5 to 7 m / s, which is at least one order of magnitude compared to the recording film material having the AgSbTe ₂ phase. It is large and has extremely excellent characteristics as a recording film material of a phase change type optical recording medium.

[0007]

However, even if the above-mentioned Au-In-Sb-Te recording film material is used, the life of repeated recording and erasing does not exceed 100,000 times at all linear velocities, and the magneto-optical Life of repeated recording and erasing of disc is 100
There was a problem that it was not always enough compared to the number of times.

The present invention has been made in view of such conventional problems,
An object of the present invention is to provide an optical recording medium having more excellent repetitive recording / erasing characteristics and a protective film for the optical recording medium suitable for the optical recording medium.

[0009]

According to the present invention, at least a first protective film, a recording film, a second protective film, and a reflective film are provided on a substrate substantially transparent to a light beam to be used. Are laminated in this order, the second protective film is made of a mixed film of ZnS and SiO ₂ , the first protective film contains nitrogen in a mixed film of ZnS and SiO ₂ , The recording film is formed so that the concentration is higher on the recording film side than on the substrate side.

[0010] The first protective layer, specifically, as in the invention according to claim 2, comprising a mixed film of ZnS and SiO ₂ on the substrate side, ZnS and SiO ₂ and the nitrogen to the recording layer side And a composite film containing ZnS, SiO _2, and nitrogen, wherein the nitrogen concentration on the substrate side of the film is substantially zero. At atomic%, the nitrogen concentration may be gradually increased from the substrate side to the recording film side.

In the optical recording medium having such a configuration, the first protective film has appropriate flexibility, and the deterioration of the protective film due to repeated heating and cooling at the time of recording and erasing is suppressed. Also, by increasing the nitrogen concentration on the recording film side, the diffusion of elements (especially sulfur) in the protective film, which adversely affects the recording film, can be effectively suppressed, and the repetitive recording and erasing characteristics of the optical recording medium are significantly improved. Can be done.

Particularly, the effect of improving the repetitive recording / erasing characteristics is that the recording film is made of Au-In-Sb.
-Te alloy, Ag-In-Sb-Te alloy, Ag-In-Sb-Te-V alloy, Cu
This is extremely remarkable in the case of chalcopyrite type compounds such as -In-Sb-Te alloy and Pd-In-Sb-Te alloy. In particular, when the recording film is made of an Au-In-Sb-Te alloy, they are represented by α, β, γ, and δ, respectively, as in the invention according to claim 5.
The composition ratio of Au, In, Sb, and Te is 0 atomic% <α ≦ 25 atomic%, 3 atomic% ≦ β ≦ 18 atomic%, 30 atomic% ≦ γ ≦ 67 atomic%, 24 atomic% ≦ δ ≦ 45 Atomic%, but 99 atomic% ≦ α +
When β + γ + δ ≦ 100 atomic%, good repetitive recording / erasing characteristics can be realized.

In the rewritable optical recording medium, the protective film is
Techniques that may contain ZnS, SiO ₂ and nitrogen (N) are disclosed in Japanese Patent Publication No. 7-111786, JP-A-6-4904, JP-A-6-3425.
No. 29, JP-A-9-198712 and the like. However, in JP-A-6-4904, ZnS and Si
Including hydrogen in addition to O ₂ and nitrogen is an essential requirement,
The constituent elements do not match those of the present invention. Also, JP-A-9-19
In the 8712 publication, it is an essential requirement that ZnS and SiO ₂ contain Si ₃ N ₄ , and the constituent materials do not match those of the present invention.

[0014] On the other hand, in Japanese Patent Publication No. 7-111786, ZnS and
SiO_TwoRecording medium comprising nitrogen as a constituent element
In addition, a protective film for an optical recording medium is disclosed. But
In Japanese Patent Publication No. 7-111786, ZnS and SiO_TwoMixed film
The protective film that contains nitrogen in the
It has been recognized that it has a concentration,
No elemental concentration distribution is provided. In the present invention,
Is a ZnS-SiO having a nitrogen concentration distribution_TwoAu-In-
Chalcopyrite type such as Sb-Te alloy, Ag-In-Sb-Te alloy
Especially rewritten when combined with recording film made of compound
It was shown that the effect of improving the service life was remarkable.
Japanese Patent Publication No. Hei 7-111786 has such descriptions and suggestions.
Absent.

[0015] Also, JP-A-6-342529 discloses a protective film.
And an auxiliary film containing nitrogen between the recording film and
A phase change optical recording medium having a wide range of components has been disclosed.
You. According to the publication, the insertion of the auxiliary layer is performed between the first protective film and the recording film.
, Or between the second protective film and the recording film.
It is recognized that it is good, and moreover,
As can be seen in the embodiment, a supplement is provided between the second protective film and the recording film.
The insertion of an auxiliary layer is mainly considered. On the other hand, the present application
In the invention, ZnS-SiO having a nitrogen concentration distribution_Two-N mixed film,
In particular, it is essential to use it for the first protective film.
It is different from the publication of Heihei 6-342529. In addition, the present invention
Then, ZnS-SiO with nitrogen concentration distribution_Two-N mixed film, Au-I
Chalcopyrite such as n-Sb-Te alloy, Ag-In-Sb-Te alloy
Rewriting especially when combined with a recording film made of a type compound
It was shown that the effect of improving the life was remarkable,
Japanese Patent Application Laid-Open No. 6-342529 shows no such description or suggestion.
Not.

In an optical recording medium used with a relative speed of recording and erasing of the recording film with respect to the light beam of 1 to 3 m / s, the values of α and β are set to 0 as in the invention according to claim 6.
Atomic% <α ≦ 25 atomic%, 7 atomic% ≦ β ≦ 18 atomic%, and when γ and δ satisfy 30 atomic% ≦ γ <45 atomic%
32 atomic% ≦ δ ≦ 45 atomic%, 45 atomic% ≦ γ <49 atomic%, 30 atomic% ≦ δ ≦ 45 atomic%, 49 atomic% ≦ γ ≦ 55 atomic%
In the case of, 35 atomic% ≤ δ ≤ 45 atomic%, provided that 99 atomic% ≤
It is preferable to use a recording film of an Au-In-Sb-Te alloy in which α + β + γ + δ ≦ 100 atomic%.

Further, in an optical recording medium used at a relative speed of 5-7 m / s at the time of recording and erasing of the recording film with respect to the light beam, the α, β,
γ and δ are 1 atomic% ≦ α ≦ 16 atomic%, 8 atomic% ≦ β
≦ 17 at%, 41 at% ≦ γ <63 at%, 24 at% ≦ δ ≦
It is preferable to use a recording film of an Au-In-Sb-Te alloy in which 36 at%, 99 at% ≦ α + β + γ + δ ≦ 100 at%. Alternatively, as in the invention according to claim 8, the values of α, β, γ, and δ are 0 atomic% <α ≦ 17 atomic%, 3 atomic% ≦ β <8 atomic%, and 51 atomic% ≦ γ ≦ 67 atomic%. Atomic%, 26 atomic% ≦ δ ≦ 33 atomic%, provided that 99 atomic% ≦ α + β + γ + δ
It is preferable to use a recording film of Au-In-Sb-Te alloy with ≤100 atomic%.

In addition, as long as the various properties of the optical recording medium are not affected, the second protective film may contain nitrogen as in the ninth aspect of the invention, At least one of the first protective film and the second protective film may further contain oxygen. Further, as in the invention according to claim 11, the mole number of SiO ₂ contained in the first protective film is preferably 10% to 40% of the mole number of ZnS in the first protective film.

In the protective film for an optical recording medium according to the twelfth aspect, nitrogen is contained in the mixed film of ZnS and SiO ₂ so that the concentration of the nitrogen is higher on one side than on the other side in the film thickness direction. It is characterized by having done. Specifically, the one side of the protective film for an optical recording medium is Zn, as in the invention according to claim 13.
It consists of a mixed film containing S, SiO ₂ and nitrogen, and the other side is Zn
A composite film composed of a mixed film of S and SiO ₂ may be used.
A mixed film containing ZnS, SiO ₂ and nitrogen as in the invention according to claim 14, wherein the nitrogen concentration on the other surface of the film is approximately 0 atomic%.
Then, the nitrogen concentration may be gradually increased toward the one side.

By using the protective film having such a configuration, the repetitive recording / erasing characteristics of the optical recording medium can be improved. Further, in the protective film for an optical recording medium of the present invention, oxygen may be contained as in the invention according to claim 15, as long as the properties of the optical recording medium are not affected. Furthermore,
As in the invention according to claim 16, the number of moles of SiO ₂ contained in the film is preferably 10% to 40% of the number of moles of ZnS.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are cross-sectional views showing preferred examples of the configuration of the optical recording medium of the present invention. The optical recording medium 1 shown in FIG. 1 has a structure in which a first protective film 3, a recording film 4, a second protective film 5, a reflective film 6, and a lacquer layer 7 are laminated on a substrate 2 in this order. , An optical recording medium for single-sided recording.

The optical recording medium 1 shown in FIG. 2 has a first protective film 3, a recording film 4, a second protective film 5, a reflective film 6, a lacquer layer 7, an adhesive layer 8, This is an optical recording medium for single-sided recording in which the upper substrate 9 is laminated in this order to increase the mechanical strength. The optical recording medium 1 shown in FIG. 3 has a first protective film 3, a recording film 4, a second
The protective film 5, the reflective film 6, and the lacquer layer 7 are laminated in this order, and the two optical recording media are bonded together via an adhesive layer 8 with the lacquer layer 7 side facing to each other, for double-sided recording. An optical recording medium. Incidentally, in the optical recording medium shown in FIGS. 2 and 3,
The lacquer layer 7 can be omitted.

In addition to the configuration examples shown in FIGS.
For the purpose of improving C / N, erasing ratio, modulation degree, recording sensitivity, life of repeated recording and erasing, etc., between the substrate 2 and the first protective film 3 of the optical recording medium 1 shown in FIGS. / Or first
Between the protective film 3 and the recording film 4, and / or between the recording film 4 and the second protective film 5, and / or between the second protective film 5 and the reflective film 6,
An optical recording medium having a configuration in which one or more auxiliary layers are inserted is also possible. In this case, the substance forming the auxiliary layer is preferably a dielectric or metal.

The substrate 2 is preferably made of a material that is transparent to the light beam to be used, for example, resin or glass, and is particularly preferably resin because it is easy to handle and inexpensive. Specific examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, and A
BS resin or the like can be used. The shape and dimensions of the substrate are not particularly limited, but are usually disk-shaped, and the thickness is usually about 0.5 to 3 mm, and the diameter is about 40 to 360 mm. A predetermined pattern such as a groove is provided on the surface of the substrate for tracking, addressing, and the like as needed.

The first protective film 3 and the second protective film 5 use the multiple reflection between the first protective film 3 and the second protective film 5 for the change in the reflectance accompanying the change in the crystal state of the recording film 4. Enlarged by
It has the effect of increasing the degree of modulation (the difference in the reflectance between the crystalline state and the amorphous state) and the effect of releasing the heat remaining in the recording film 4 at an appropriate rate by heat conduction during recording. The first protective film 3 is formed such that a mixed film of ZnS and SiO ₂ contains nitrogen (N), and the nitrogen concentration is higher on the recording film 4 side than on the substrate 2 side. Specifically, for example, ZnS and SiO _{2 are provided} on the substrate side.
Or a composite film having a mixed film containing ZnS, SiO ₂ and nitrogen on the recording film side, or
A mixed film containing ZnS, SiO ₂ and nitrogen.
The nitrogen concentration on the side surface is set to approximately 0 atomic%, and the nitrogen concentration is gradually increased from the substrate 2 side toward the recording film 4 side.
Incidentally, the gradual increase in the concentration means that the concentration never decreases (it may remain at a constant value). Further, the number of moles of SiO ₂ contained in the first protective film 3 is as follows:
It is preferably 10% to 40% of the number of moles of ZnS. SiO ₂
If the number of moles is less than 10%, the crystal grain size increases, and the denseness of the film deteriorates. On the other hand, if it exceeds 40%, the refractive index of the mixed film becomes small, which is not preferable from the viewpoint of optical characteristics.

A mixed film of ZnS and SiO _{2 in which} the molar ratio of ZnS and SiO ₂ is given in the above range is substantially transparent to a light beam having a wavelength of 350 nm to 850 nm usually used for an optical recording medium. It has an excellent performance as a protective film for optical recording media, such as having a higher melting point than the film material and having a suitable hardness and flexibility. However, the protection film deteriorates due to repeated heating and cooling during recording and erasing, and the elements (especially sulfur) in the protection film diffuse into the recording film to deteriorate the performance of the recording film. However, the number of repetitions of recording and erasing of the optical recording medium is limited. In particular, the limit of the recording and erasing repetition life related to the protective film is remarkable when a chalcopyrite-type compound such as an Ag-In-Sb-Te alloy or an Au-In-Sb-Te alloy is used for the recording film. When a protective film composed of ZnS and SiO ₂ is used in combination with a recording film composed of a Ge-Sb-Te alloy, recording and erasing can be repeated about 100,000 times, whereas a chalcopyrite type When used in combination with a recording film made of a compound, the repetition life was limited to 1,000 to tens of thousands of times. Since the deterioration of the protective film due to repeated heating and cooling should have occurred regardless of the type of recording film, the difference in the repeated life between the Ge-Sb-Te alloy and the chalcopyrite-type compound was Ge-Sb-Te It is considered that the recording film made of an alloy does not deteriorate much due to diffusion mixing with the element (especially, sulfur) in the protective film, whereas the recording film made of a chalcopyrite-type compound deteriorates greatly.

Conventionally, in order to solve such a problem,
A method has been considered in which nitrogen is contained in a mixed film of ZnS and SiO ₂ to form a dense film with few defects. However, even if nitrogen is uniformly contained in the entire first protective film 3, the first protective film 3
The effect of preventing the diffusion of the elements in the recording film is low. In addition, when nitrogen is uniformly contained in the entire first protective film 3, the entire film becomes hard, and the flexibility of the film is rather reduced. For this reason, the durability of the first protective film 3 is reduced with respect to the repetition of expansion and contraction caused by heating and cooling of the recording film 4.

Therefore, in the present embodiment, a nitrogen concentration distribution in the film thickness direction is introduced into the first protective film 3 so that the first protective film 3 is provided with a hard portion and a flexible portion, so that the first protective film 3 expands and contracts during recording / erasing. The deterioration of the first protective film 3 due to the above is prevented. In addition, in order to prevent diffusion of elements (especially sulfur) in the first protective film 3 into the recording film 4, the nitrogen concentration near the recording film 4 was increased. By providing such a nitrogen concentration distribution,
The diffusion of sulfur and the like is effectively prevented, and is particularly remarkable in the optical recording medium 1 using the recording film 4 made of a chalcopyrite-type compound such as an Ag-In-Sb-Te alloy or an Au-In-Sb-Te alloy. It is possible to realize an improvement of the life expectancy repeatedly.

The first protective film 3 can be manufactured by, for example, the following two methods. In the first method, first, a ZnS—SiO ₂ target is sputtered in an Ar gas atmosphere to form a mixed film of ZnS and SiO ₂ on the substrate 2 with an appropriate thickness. After that, gradually add N ₂ gas to Ar gas,
Sputtering (reactive sputtering) is continued while gradually increasing the partial pressure of the N ₂ gas to form a ZnS—SiO ₂ —N mixed film. At this time, the method of increasing the partial pressure of the N ₂ gas may be a monotonous increase at a fixed ratio or a stepwise increase. The nitrogen concentration distribution in the first protective film 3 is determined by how to increase the partial pressure of N ₂ gas. In the second method, after a mixed film of ZnS and SiO ₂ is formed on the substrate 2 in the same manner as the first method, the substrate 2 is transferred to another chamber having a constant concentration of Ar + N ₂ gas atmosphere, and the ZnS-SiO 2 Reactive sputtering is performed using _two targets to form a ZnS—SiO ₂ —N mixed film. Further, if necessary, Ar + N ₂ having a higher N ₂ gas concentration may be used.
Reactive sputtering is continued while the substrate 2 is moved to a chamber having a gas atmosphere a required number of times, and a ZnS—SiO ₂ —N mixed film having an increased nitrogen concentration is formed into a multilayer film. In both of the above two methods, the partial pressure of N ₂ gas in the atmosphere gas is 0.01 Pa or more.
It is preferably at most 7 Pa. If it is smaller than this, the effect of mixing nitrogen into the first protective film 3 will not be exhibited. On the other hand, if it is larger than this, the film forming efficiency is reduced.

In order to form the first protective film 3, in addition to the above methods, a vacuum evaporation method, a plasma
It may be formed by a vapor phase growth method such as a CVD method, a photo CVD method, and an electron beam evaporation method. The first protective film 3 may contain other elements such as oxygen, hydrogen, carbon, and fluorine as far as the influence is small. From the viewpoint of the optical characteristics of obtaining a high degree of modulation, the thickness of the first protective film 3 is preferably 50 to 300 nm. Further, the thickness of the portion of the first protective film 3 not containing nitrogen is preferably at least 30 nm or more. If the thickness is smaller than this, the flexibility of the film decreases, and the durability of the film to repeated expansion and contraction decreases.

The second protective film 5 is a mixed film containing ZnS and SiO ₂ . At this time, for the same reason as in the first protective film 3, the number of moles of SiO ₂ contained in the second protective film 5 is Zn
Preferably, it is 10% to 40% of the number of moles of S 2. The second protective film 5 is formed by a sputtering method, a vacuum evaporation method, a plasma CVD method,
It can be formed by a vapor phase growth method such as a photo CVD method and an electron beam evaporation method. The second protective film 5 may include other elements such as nitrogen, oxygen, hydrogen, carbon, and fluorine, as long as the performance is not significantly reduced.

Even if a ZnS—SiO ₂ —N mixed film having a nitrogen concentration distribution as used in the first protective film 3 is used for the second protective film 5, a large improvement in the repetitive recording / erasing characteristics cannot be expected. Because the second protective film 5 is in contact with the reflective film 6 having a high heat dissipation effect, the temperature does not become much higher than that of the first protective film 3, and therefore, the second protective film 5 originally moves from the second protective film 5 to the recording film 4. This is because diffusion of the element (particularly sulfur) does not occur so frequently. Of course, the disk characteristics using a mixed film of the first protective layer 3 with ZnS-SiO ₂ -N used in the second protective film 5 is not reduced, the benefits for the production process becomes complicated less.

From the viewpoint of the optical characteristics of obtaining a high degree of modulation, the thickness of the second protective film 5 is 10 to 60 nm or 100 to 250 nm.
It is preferred that Thermally, when the thickness of the second protective film 5 is small, the effect of insulating the space between the recording film 4 and the reflective film 6 is reduced, and the heat stored in the recording film 4 during recording has a high heat radiation effect. It quickly dissipates in the reflection film 6. Therefore, 10 ~
In order to realize recording and erasing on the optical recording medium 1 having the second protective film 5 as thin as about 60 nm, the recording film material needs to have high sensitivity to heating by laser light.

Conventionally, in an optical recording medium using a chalcogen-based recording material such as Ge-Sb-Te, the thickness of the second protective film 5 is set to 100 to 250 nm because the recording film material does not have sufficient sensitivity.
The structure was taken. On the other hand, Au-In-Sb-Te alloy and Ag-In-Sb-Te alloy recording film materials have high sensitivity to heating by laser light.
In the optical recording medium used for the above, the thickness of the second protective film 5 is
It can be 10 to 60 nm. This structure is of a quenching type in which the cooling rate of the recording film 4 at the time of recording is high, so that the edges of the recording marks become clear, the recording density can be increased, and the jitter is reduced. There is. Further, since the film thickness is small, the time for forming the second protective film 5 by sputtering or the like can be reduced, which leads to an improvement in productivity.

The recording film 4 is made of a Ge—Sb—Te alloy, Pd—Ge—Sb—T
e alloys and other chalcogen-based compounds can also be used, but Au-In-Sb-Te alloys and Ag-I
It is preferable to use chalcopyrite-based compounds such as an n-Sb-Te alloy, an Ag-In-Sb-Te-V alloy, a Cu-In-Sb-Te alloy, and a Pd-In-Sb-Te alloy. Moreover, the first protective film is made of ZnS-SiO ₂
The effect of the -N composite film is remarkable when the chalcopyrite-based compound is used for the recording film, and a remarkable improvement in the recording / erasing repetition performance can be obtained. Although the thickness of the recording film 4 is not particularly limited, it is usually 10 to 200 nm, in particular, in order to realize a high reflectance and a high degree of modulation (a large difference in reflectance between a recorded state and an unrecorded state). It is preferably 15 to 150 nm. The method for forming the recording film 4 is not particularly limited,
Sputtering method, vacuum evaporation method, plasma CVD method, light CVD method,
It is preferably formed by a vapor phase growth method such as an electron beam evaporation method.

When an Au—In—Sb—Te alloy is used for the recording film 4, Au, In, and α represented by α, β, γ, and δ, respectively.
When the composition ratio of Sb and Te is 0 atomic% <α ≦ 25 atomic%, 3
Atomic% ≦ β ≦ 18 atomic%, 30 atomic% ≦ γ ≦ 67 atomic%, 24 atomic% ≦ δ ≦ 45 atomic% (however, 99 atomic% ≦ α + β + γ +
δ ≦ 100 atomic%). In particular, the relative speed at the time of recording / erasing of the recording film with respect to the light beam is 1-3 m / s
In the optical recording medium used in the above, α and β are:
0 atomic% <α ≦ 25 atomic%, 7 atomic% ≦ β ≦ 18 atomic%, and when γ and δ satisfy 30 atomic% ≦ γ <45 atomic%
32 atomic% ≦ δ ≦ 45 atomic%, 45 atomic% ≦ γ <49 atomic%, 30 atomic% ≦ δ ≦ 45 atomic%, 49 atomic% ≦ γ ≦ 55 atomic%
In the case of, 35 atomic% ≤ δ ≤ 45 atomic%, provided that 99 atomic% ≤
It is preferable that α + β + γ + δ ≦ 100 atomic%. In an optical recording medium used at a relative speed of 5-7 m / s at the time of recording and erasing of the recording film with respect to the light beam, α, β, γ, and δ are such that 1 atomic% ≦ α ≦ 16 atomic% , 8 atomic% ≦ β ≦ 17 atomic%, 41 atomic% ≦ γ <63 atomic%, 24 atomic% ≦ δ ≦ 36 atomic%, provided that 99 atomic% ≦ α + β + γ + δ
≦ 100 at%, or when α, β, γ, and δ are 0
Atomic% <α ≦ 17 atomic%, 3 atomic% ≦ β <8 atomic%, 51 atomic% ≦ γ ≦ 67 atomic%, 26 atomic% ≦ δ ≦ 33 atomic%, provided that 99 atomic% ≦ α + β + γ + δ ≦ 100 atomic% It is preferred that If the composition is out of the above range, good repetitive recording / erasing characteristics cannot be obtained.

The composition of the recording film 4 is easily measured by an X-ray microanalyzer, and the composition is determined by this method also in the present embodiment. In addition, fluorescent X
Analytical methods such as X-ray, Rutherford backscattering, Auger electron spectroscopy, and emission analysis are conceivable, but when using them, it is necessary to calibrate with a value obtained by an X-ray microanalyzer.

Although the material of the reflection film 6 is not particularly limited, it is usually a high-reflectivity metal such as Al, Au, Ag, Pt, Cu or the like or an alloy containing at least one of these, or Si, Si nitride. ,
What is necessary is just to comprise from high-reflectivity semiconductors, such as SiC. It is preferable that the thickness of the reflection film 6 be 30 to 300 nm. Thickness
If it is less than 30 nm, it becomes difficult to obtain a sufficient reflectance, and the effect of releasing the heat remaining on the recording film 4 during recording is reduced. Further, even if it exceeds 300 nm, no remarkable improvement in the reflectance and the heat emission effect is observed. The reflective film 6 is preferably formed by a vapor phase growth method such as a sputtering method or a vapor deposition method.

The lacquer layer 7 is provided for improving scratch resistance and corrosion resistance. The lacquer layer 7 is preferably composed of various organic substances, but is particularly preferably composed of a substance obtained by curing a radiation-curable compound or a composition thereof by radiation such as an electron beam or ultraviolet rays. preferable. The thickness of the lacquer layer 7 is usually about 0.1 to 100 μm, and may be formed by a usual method such as spin coating, gravure coating, spray coating and the like.

The adhesive layer 8 is desirably made of various organic materials, but is preferably made of a thermoplastic material, a sticky material,
The radiation-curable compound or the composition thereof is preferably composed of a substance cured by an electron beam or radiation. The thickness of the adhesive layer 8 is usually about 0.1 to 100 μm, and may be formed by an optimum method selected according to the material constituting the adhesive layer 8, for example, spin coating, gravure coating, spray coating, roll coating, or the like. .

The upper substrate 9 can be made of the same resin as the substrate 2 described above. Generally, at the time of manufacturing a phase-change optical recording medium, the recording film 4 is in an amorphous state,
In order to obtain an overwritable optical recording medium, it is necessary to crystallize (initialize) the recording film 4 by some method. As a method for initializing the optical recording medium 1, various methods such as a method using a semiconductor laser, a method using an Ar laser, and a method using a flash lamp can be used. [Examples] Next, the present invention will be described in more detail with reference to specific examples of the present invention. However, these examples do not limit the present invention in any way.

(Examples 1 to 4) 120 mm in diameter and 1.2 mm in thickness
An optical recording medium having the configuration of FIG. 1 is formed by forming a first protective film 3, a recording film 4, a second protective film 5, a reflective film 6, and a lacquer layer 7 in this order on a grooved polycarbonate substrate 2. It was set to 1. The groove of the substrate 2 has a track pitch of 1.
6 μm, width 0.5 μm, and depth 50 nm.

The first protective film 3 is made of ZnS-SiO ₂ (SiO ₂ : 20 mol
%) As a target, and was prepared by the following method by a sputtering method. First, a ZnS-SiO ₂ film is formed by an RF sputtering method in an Ar gas atmosphere, and when the thickness reaches about 190 nm, a mixed gas of Ar and N ₂ is injected as an atmosphere gas to perform RF sputtering (RF reactivity). The sputtering was continued to form a composite film having a total thickness of 197 nm. The partial pressures of the Ar gas and the N ₂ gas in the mixed gas injected at this time are 0.36 Pa and 0.18 Pa, respectively.
Met.

The recording film 4 is composed of an In-Sb-Te target on which In,
Each of Sb, Te, Ag, Cu, Pd, and V chips was mounted thereon, and the composition was changed by a DC sputtering method. The thickness of the recording film 4 was 20 nm. The composition of the recording film 4 was measured by an X-ray microanalyzer using an EDAX device system manufactured by Philips. That is, a recording film 4 having a thickness of about 50 nm was formed on a polycarbonate flat plate by a sputtering method, and the energy spectrum of the sample was detected by an X-ray microanalyzer. The background of the polycarbonate flat plate and the like was removed from the detected energy spectrum, and the energy spectrum of only the recording film 4 was derived. The constituent elements of the recording film 4 were quantified from this energy spectrum, and the composition of the recording film 4 was determined.

The second protective film 5 is made of ZnS-SiO ₂ (SiO ₂ : 20 mol
%) As a target by RF sputtering in an Ar gas atmosphere. The thickness of the second protective film 5 was 20 nm.
The reflection film 6 was formed by a DC sputtering method using Al as a target. The thickness was 75 nm. The lacquer layer 7 was formed by applying an ultraviolet curable resin by a spin coating method and then curing the applied resin by irradiation with ultraviolet light. Lacquer layer 7 after curing
Had a thickness of 10 μm.

The recording film 4 after the production of the optical recording medium 1 was amorphous. For this reason, the recording film 4 was sufficiently crystallized by a high-power semiconductor laser beam having a wavelength of 810 nm to be in an initialized state. The evaluation of the optical recording medium 1 was performed by irradiating a semiconductor laser beam having a wavelength of 780 nm from the substrate 2 side through an objective lens having an NA of 0.5 and narrowing the surface of the recording film 4 to a spot diameter of about 1 μm. At the time of recording, recording was performed by changing the irradiation laser pulse to multi-pulse. The recording power was 13 mW, the erasing power was 6 mW, the bottom power of the multi-pulse was 1 mW, and the reproducing power was 1 mW.

As the disk characteristics, the life of repeated recording and erasing was measured by the following method. That is, the repetitive recording and erasing characteristics are as follows: a random signal of the EFM modulation method is repeatedly overwritten at a linear velocity of 2.8 m / s, reproduced at a linear velocity of 1.4 m / s for each predetermined number of overwrites, and the jitter of the 3T signal is reduced It was measured. The number of times that jitter exceeds 35 ns is defined as the life of repeated recording and erasing, and is shown in a certain range, for example, "1,000 to 10,000". This indicates that the characteristics can be changed within the indicated range depending on manufacturing conditions and evaluation conditions.

Table 1 shows the composition of the recording film and the disc characteristics of the optical recording media of Examples 1 to 4 produced by such a method. (Comparative Example 1-4) The first protective layer 3, an optical recording medium was prepared the way except for forming without injecting a mixed gas of Ar and N ₂ in the same manner as in Example 1-4. At this time, the first protection film 3 was a ZnS-SiO ₂ (SiO ₂ : 20 mol%) mixed film having a thickness of 197 nm. Table 1 shows the recording film composition and the disc characteristics of the optical recording media of Comparative Examples 1 to 4 manufactured by such a method.

[0049]

[Table 1]

The optical recording media of Examples 1 to 4
It can be seen that the repetitive recording / erasing characteristics are improved as compared with the optical recording media of the corresponding recording film compositions in Comparative Examples 1 to 4. Thus, it is clear that the recording and erasing characteristics of the optical recording medium are significantly improved by including nitrogen in the first protective film 3. (Embodiment 5) The recording film 4 was formed on an In-Sb-Te target by using In,
An optical recording medium was manufactured in the same manner as in Example 1 except that each chip of Sb, Te, and Au was mounted and manufactured by DC sputtering.

(Comparative Example 5) A recording film 4 was produced in the same manner as in Comparative Example 1 except that each of In, Sb, Te, and Au chips was mounted on an In-Sb-Te target by DC sputtering. An optical recording medium was manufactured, and Comparative Example 5 was obtained. Table 2 shows the recording film compositions and disc characteristics of the optical recording media of Example 5 and Comparative Example 5 produced by such a method.

[0052]

[Table 2]

Also in this case, it can be seen that the optical recording medium of Example 5 has improved repetitive recording / erasing characteristics as compared with the optical recording medium of Comparative Example 5. In addition, comparing Example 5 with Examples 1 to 4 in Table 1, it can be seen that when the Au—In—Sb—Te alloy is used for the recording film 4, the recording / erasing characteristics are particularly improved. (Example 6) An optical recording medium was produced in the same manner as in Example 5, except that the first protective film 3 was produced by the following method.

That is, ZnS—SiO ₂ (SiO ₂ : 20 mol%) was targeted and RF sputtering was performed in an Ar gas atmosphere.
A ZnS—SiO ₂ film having a thickness of 0 nm is formed on the substrate 2. The disk was transferred to a chamber in which a mixed gas of Ar and N ₂ was flowed as an atmospheric gas, and RF-reactive sputtering was performed using ZnS-SiO ₂ (SiO ₂ : 20 mol%) as a target to obtain a ZnS-SiO _{2 having a} thickness of 10 nm. -N
A film was formed. At this time, the partial pressures of the Ar gas and the N ₂ gas were 0.36 Pa and 0.18 Pa, respectively.

(Example 7) An optical recording medium was produced in the same manner as in Example 5, except that the first protective film 3 was produced by the following method. That is, the target is ZnS-SiO ₂ (SiO ₂ : 20 mol%), and the target is 150 nm by RF sputtering in an Ar gas atmosphere.
A thick ZnS—SiO ₂ film is formed on the substrate 2. That disk
Transfer to a chamber in which a mixed gas of Ar and N ₂ flows as an atmospheric gas, perform RF reactive sputtering using ZnS-SiO ₂ (SiO ₂ : 20 mol%) as a target, and obtain a ZnS-SiO ₂ -N film with a thickness of 30 nm. Was formed. At this time, the partial pressures of Ar gas and N ₂ gas are respectively
It was 0.45 Pa and 0.09 Pa. Further, the disk was transferred to a chamber in which a mixed gas of Ar and N ₂ having different concentrations was flowed as an atmospheric gas, and RF reactive sputtering was performed using ZnS-SiO ₂ (SiO ₂ : 20 mol%) as a target to obtain a 10 nm thick film. ZnS-SiO ₂
An -N film was formed. At this time, the partial pressures of the Ar gas and the N ₂ gas were 0.36 Pa and 0.18 Pa, respectively. In this way 19
A 0 nm composite film was formed.

(Embodiment 8) The second protective film 5 is made of ZnS-SiO
Example 5 except that a ZnS—SiO ₂ —N film having a thickness of 20 nm was formed by RF reactive sputtering in a mixed gas atmosphere of Ar and N _{2 using 2} (SiO ₂ : 20 mol%) as a target. An optical recording medium was formed in the same manner as described above. At this time, the partial pressures of the Ar gas and the N ₂ gas were 0.36 Pa and 0.18 Pa, respectively.

(Embodiment 9) The first protective film 3 is made of ZnS-SiO
_{Using 2} (SiO ₂ : 20 mol%) as a target, an optical recording medium was produced in the same manner as in Example 5, except that the optical recording medium was produced by the following method. First, a ZnS-SiO ₂ film was formed by an RF sputtering method in an Ar gas atmosphere, and when the thickness reached about 190 nm, a mixed gas of Ar, N ₂ and O ₂ was injected as an atmosphere gas to perform RF sputtering ( (RF reactive sputtering) was continued to form a ZnS—SiO ₂ —NO composite film having a total thickness of 197 nm. At this time, the partial pressures of the Ar gas, the N ₂ gas, and the O ₂ gas in the injected mixed gas were 0.36 Pa, 0.18 Pa, and 0.05 Pa, respectively.

Table 2 shows the recording film composition and disk characteristics of each of the optical recording media of Examples 6 to 9 produced by the above-described methods. (Comparative Example 6) An optical recording medium was manufactured in the same manner as in Comparative Example 5, except that the second protective film 5 was manufactured by the following method.

First, in a mixed gas atmosphere of Ar and N ₂ gas, R
A ZnS-SiO ₂ -N film is formed by the F reactive sputtering method, and when the thickness reaches about 10 nm, RF sputtering is continued using only Ar gas as an atmosphere gas to form a composite film having a total thickness of 20 nm. Formed. At this time, the partial pressures of the Ar gas and the N ₂ gas in the mixed gas were 0.36 Pa and 0.18 Pa, respectively. (Comparative Example 7) ZnS-SiO ₂ (SiO ₂ : 20)
mol%) in a mixed gas atmosphere of Ar and N ₂ gas, and an RF recording medium was produced in the same manner as in Example 5. In this optical recording medium, the first protective film 3 is a 197 nm thick ZnS-SiO ₂ -N film having a uniform nitrogen concentration distribution in the film thickness direction.

Table 2 shows the recording film composition and disk characteristics of each of the optical recording media of Comparative Examples 6 and 7 produced by the above-described methods. The above Examples 6 to 9 are Comparative Examples 6 and 7
It can be seen that all of them show better repetitive recording and erasing characteristics as compared with. In Comparative Example 6 in which only the second protective film 5 contained nitrogen, the same recording and erasing characteristics as in Comparative Example 5 were exhibited, and in comparison with Examples 5 to 9 in which nitrogen was contained in the first protective film 3 side. No remarkable improvement in the repetitive recording / erasing characteristics is observed. Thus, it is understood that even if nitrogen is contained in the second protective film 5, the effect of improving the recording and erasing characteristics is not so much obtained.
The repetitive recording and erasing characteristics of Comparative Example 7 in which nitrogen was uniformly contained in the first protective film 3 were improved compared to Comparative Example 5, but the remarkable improvements of Examples 5 to 9 were observed. Absent. Thus, it is found that giving the first protective film 3 a nitrogen concentration distribution is effective for improving the recording / erasing characteristics.

(Examples 10 and 11) The recording film 4 was manufactured by the DC sputtering method while placing the In, Sb, Te, and Au chips on an In-Sb-Te target and varying the composition. An optical recording medium was manufactured in the same manner as in Example 1, and Example 10 and Example 11 were performed. (Comparative Examples 8 to 10) Except that the composition of the recording film 4 was changed,
Optical recording media were produced in the same manner as in Examples 10 and 11, and Comparative Examples 8 to 10 were produced.

Table 2 shows the composition of the recording films and the disk characteristics of the optical recording media of Examples 10 and 11 and Comparative Examples 8 to 10 produced by such a method. From Table 2, the composition ratio of Au, In, Sb, and Te represented by α, β, γ, and δ is 0 atomic%.
<Α ≦ 25 atomic%, 7 atomic% ≦ β ≦ 18 atomic%, 30 atomic% ≦
32 atomic% ≦ δ ≦ 45 atomic% when γ <45 atomic%, 30 atomic% ≦ δ ≦ 45 atomic% when 45 atomic% ≦ γ <49 atomic%, 49
Examples 5 to 11 satisfying 35 atom% ≦ δ ≦ 45 atom% when atomic% ≦ γ ≦ 55 atom%, and satisfying 99 atom% ≦ α + β + γ + δ ≦ 100 atom%, show good repetitive recording / erasing characteristics. It can be seen that Comparative Examples 8 to 10 in which the composition ratio is not in the above range do not exhibit good repetitive recording / erasing characteristics.

Example 12 A first protective film 3, a recording film 4, a second protective film 5, and a polycarbonate film 2 having lands / grooves having a diameter of 120 mm and a thickness of 0.6 mm were provided on two polycarbonate substrates 2 respectively. A reflective film 6 and a lacquer layer 7 are laminated in this order,
The two optical recording media were joined via an adhesive layer 8 with the lacquer layer 7 facing the other side, and an optical recording medium 1 having the configuration of FIG. 3 was obtained. The land / groove of the substrate 2 had a track pitch of 0.74 μm and a depth of 70 nm.

The first protective film 3 is made of ZnS-SiO ₂ (SiO ₂ : 20 mol
%) As a target, and was prepared as follows by a sputtering method. First, a ZnS-SiO ₂ film was formed by an RF sputtering method in an Ar gas atmosphere, and when the thickness reached about 133 nm, a mixed gas of Ar and N ₂ was injected as an atmosphere gas to perform RF sputtering (RF reactivity). Sputtering was continued to form a ZnS—SiO ₂ —N mixed film having a total thickness of 140 nm. At this time, the partial pressures of the Ar gas and the N ₂ gas in the injected mixed gas are each 0.
It was 36 Pa and 0.18 Pa.

The recording film 4 was produced in the same manner as in Example 5 except that the thickness was set to 22 nm. The second protective film 5 has a thickness of 25
Except for nm, it was produced in the same manner as in Example 1. The reflection film 6 was produced in the same manner as in Example 1 except that the thickness was 100 nm. The lacquer layer 7 was produced in the same manner as in Example 1. The adhesive layer 8 was formed by applying an ultraviolet curable resin by a screen coating method and then curing the applied resin by irradiation with ultraviolet light. The thickness of the adhesive layer 8 after curing was 30 to 50 μm.

The recording film 4 after the production of the optical recording medium 1 was amorphous. For this reason, the recording film 4 was sufficiently crystallized by a high-power semiconductor laser beam having a wavelength of 810 nm to be in an initialized state. The evaluation of the optical recording medium 1 was performed by irradiating a semiconductor laser beam having a wavelength of 635 nm from the substrate 2 side through an objective lens with NA = 0.6 and narrowing the surface of the recording film 4 to a spot diameter of about 1 μm. At the time of recording, recording was performed by changing the irradiation laser pulse to multi-pulse. The recording power was 12 mW, the erasing power was 6 mW, the bottom power of the multi-pulse was 1 mW, and the reproducing power was 1 mW.

As the disk characteristics, the life of repeated recording and erasing was measured by the following method. That is, the repetitive recording / erasing characteristics are as follows: the random signal of the 8/16 modulation method is repeatedly overwritten at a linear velocity of 6.0 m / s, and the linear signal is reproduced at a linear velocity of 6.0 m / s for each predetermined number of overwrites. Jitter was measured. Jitter is the reference clock (34.27ns)
The number of times of overwriting until exceeding 15% was defined as the life of repeated recording and erasing.

(Comparative Example 11) The first protective film 3 was
An optical recording medium was produced in the same manner as in Example 12, except that the optical recording medium was formed without injecting the N ₂ mixed gas. At this time, the first protective film 3 was a ZnS-SiO ₂ (SiO ₂ : 20 mol%) mixed film having a thickness of 140 nm. Table 3 shows recording film compositions and disk characteristics of the optical recording media of Example 12 and Comparative Example 11 manufactured by the above-described methods.

[0069]

[Table 3]

It can be seen that the optical recording medium of Example 12 has improved repetitive recording / erasing characteristics as compared with the optical recording medium of Comparative Example 11. (Examples 13 and 14) The recording film 4 was placed on an In-Sb-Te target.
Place the In, Sb, Te, and Au chips and shake the composition while
Optical recording media were produced in the same manner as in Example 12, except that the optical recording medium was produced by the C sputtering method, and Examples 13 and 14 were produced.

(Comparative Examples 12 to 14) Optical recording media were produced in the same manner as in Examples 13 and 14 except that the composition of the recording film 4 was changed, and Comparative Examples 12 and 14 were made. Table 3 shows the recording film compositions and disk characteristics of the optical recording media of Examples 13 and 14 and Comparative Examples 12 to 14 manufactured in such a manner.

From Table 3, the composition ratio of Au, In, Sb, and Te represented by α, β, γ, and δ is 1 atomic% ≦
α ≦ 16 atomic%, 8 atomic% ≦ β ≦ 17 atomic%, 41 atomic% ≦ γ
≦ 63 at%, 24 at% ≦ δ ≦ 36 at%, or 0 at% <α ≦ 17 at%, 3 at% ≦ β <8 at%, 51 at%
≦ γ ≦ 67 at%, 26 at% ≦ δ ≦ 33 at%, but 99
Example 12 where atomic% ≦ α + β + γ + δ ≦ 100 atomic%
Nos. To 14 show good repetitive recording and erasing characteristics, but Comparative Examples 12 to 14 whose composition ratios are not in the above range do not show good repetitive recording and erasing characteristics.

[0073]

As described above, claims 1 to 3 and 9
According to the inventions of Nos. 1 to 11, there is an effect that an optical recording medium with improved repeated recording / erasing characteristics can be obtained. According to the fourth aspect of the present invention, the recording and erasing characteristics of the optical recording medium can be further improved by using a chalcopyrite-type compound for the recording film.

According to the fifth to eighth aspects of the present invention,
When an Au-In-Sb-Te alloy among chalcopyrite type compounds is used for the recording film, the recording / erasing characteristics can be remarkably improved by limiting the composition ratio to a specific range. Claim
According to the inventions according to the inventions 12 to 16, by improving the repetitive recording and erasing characteristics of the optical recording medium, the mixed film of ZnS and SiO ₂ is provided with a concentration distribution to form a protective film for the optical recording medium containing nitrogen. Can be done.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a film configuration of an optical recording medium according to the present invention.

FIG. 2 is a sectional view showing another example of the film configuration of the optical recording medium of the present invention.

FIG. 3 is a sectional view showing still another example of the film configuration of the optical recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical recording medium 2 Substrate 3 First protective film 4 Recording film 5 Second protective film 6 Reflective film 7 Lacquer layer 8 Adhesive layer 9 Upper substrate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C23C 14/06 B41M 5/26 X

Claims (16)

[Claims] 1. An optical recording medium comprising a substrate substantially transparent to a light beam to be used and at least a first protective film, a recording film, a second protective film, and a reflective film deposited in this order. The protective film is made of a mixed film of ZnS and SiO ₂ , the first protective film contains nitrogen in a mixed film of ZnS and SiO ₂ ,
An optical recording medium, wherein the nitrogen concentration is higher on the recording film side than on the substrate side. 2. The method according to claim 1, wherein the first protective film is formed of ZnS and Si on the substrate side.
_2. The optical recording medium according to claim 1, wherein the optical recording medium is a composite film having a mixed film of O _{2 and} a mixed film containing ZnS, SiO ₂ and nitrogen on the recording film side. 3. The first protective film comprises a mixed film containing ZnS, SiO ₂ and nitrogen, wherein the nitrogen concentration on the surface of the mixed film on the substrate side is approximately 0 atom%, and 2. The optical recording medium according to claim 1, wherein the nitrogen concentration is gradually increased toward. 4. The recording film is made of an Au-In-Sb-Te alloy, an Ag-In-
2. The alloy according to claim 1, wherein the alloy comprises one of an Sb-Te alloy, an Ag-In-Sb-Te-V alloy, a Cu-In-Sb-Te alloy, and a Pd-In-Sb-Te alloy.
4. The optical recording medium according to any one of items 3 to 3. 5. The recording film according to claim 1, wherein the recording film is made of an Au—In—Sb—Te alloy, and is represented by α, β, γ, and δ, respectively.
The composition ratio of Sb and Te is 0 atomic% <α ≦ 25 atomic%, 3 atomic% ≦ β ≦ 18 atomic%, 30 atomic% ≦ γ ≦ 67 atomic%, 24 atomic% ≦ δ ≦ 45 atomic%, 5. The optical recording medium according to claim 4, wherein: 99 atomic% ≦ α + β + γ + δ ≦ 100 atomic%. 6. An optical recording medium in which the relative speed of recording and erasing of a recording film with respect to a light beam is 1 to 3 m / s, wherein α and β are 0 atomic% <α ≦ 25 atomic%. 7 atomic% ≦ β ≦ 18 atomic%, and when γ and δ are 30 atomic% ≦ γ <45 atomic%, 32 atomic% ≦ δ ≦ 45 atomic% and 45 atomic% ≦ γ <49 Atomic%, 30 atomic% ≦ δ ≦ 45 atomic%, 49 atomic% ≦ γ ≦ 55 atomic%, 35 atomic% ≦ δ ≦ 45 atomic%, but 99 atomic% ≦ α + β + γ + δ ≦ 100 atomic%. 6. The optical recording medium according to claim 5, wherein: 7. In an optical recording medium used with a relative velocity of 5-7 m / s at the time of recording / erasing of a recording film with respect to a light beam, said α, β, γ, and δ are 1 atomic% ≦ α ≦ 16 atomic%, 8 atomic% ≦ β ≦ 17 atomic%, 41 atomic% ≦ γ <63 atomic%, 24 atomic% ≦ δ ≦ 36 atomic%, where 99 atomic% ≦ α + β + γ + δ ≦ 100 atomic% The optical recording medium according to claim 5, wherein: 8. In an optical recording medium used at a relative speed of 5-7 m / s at the time of recording and erasing of a recording film with respect to a light beam, α, β, γ, and δ are 0 atomic% < α ≦ 17 atomic%, 3 atomic% ≦ β <8 atomic%, 51 atomic% ≦ γ ≦ 67 atomic%, 26 atomic% ≦ δ ≦ 33 atomic%, where 99 atomic% ≦ α + β + γ + δ ≦ 100 atomic% The optical recording medium according to claim 5, wherein: 9. The optical recording medium according to claim 1, wherein said second protective film contains nitrogen. 10. The optical recording medium according to claim 1, wherein at least one of the first protective film and the second protective film contains oxygen. 11. The method according to claim 1, wherein the number of moles of SiO ₂ contained in the first protective film is 10% to 40% of the number of moles of ZnS in the first protective film. An optical recording medium according to claim 1. 12. A protective film for an optical recording medium, wherein a mixed film of ZnS and SiO ₂ contains nitrogen, and the concentration of the nitrogen is higher on one side than on the other side in the film thickness direction. 13. The protection for an optical recording medium according to claim 12, wherein the one side is a composite film including ZnS, SiO ₂ and nitrogen and the other side is a composite film including ZnS and SiO _2. film. 14. A mixed film containing ZnS, SiO ₂ and nitrogen, wherein
13. The protective film for an optical recording medium according to claim 12, wherein the nitrogen concentration on the other side of the film is approximately 0 atomic%, and the nitrogen concentration gradually increases toward the one side. 15. The protective film for an optical recording medium according to claim 12, comprising oxygen. 16. The protective film for an optical recording medium according to claim 12, wherein the number of moles of SiO ₂ contained in the film is 10% to 40% of the number of moles of ZnS.