JPS63195841A - Optical recording medium - Google Patents

Abstract

PURPOSE:To prevent deterioration of a recording layer and to the corrosion resistance and durability thereof by providing a specific org. protective coating layer so as to completely cover a laminate formed by disposing a 1st inorg. protective layer, recording layer and 2nd inorg. protective layer successively on a substrate. CONSTITUTION:This optical recording medium is constituted by disposing the 1st inorg. protective layer 5, a thin magnetic film layer 4 as the recording layer and the 2nd inorg. protective layer 5 successively on the substrate 2 to form the laminate and forming the org. protective coating layer so as to completely cover the laminate. The moisture permeation rate T at 40 deg.C of the 2nd inorg. protective layer 5 of the above-mentioned optical recording medium is preferably set at <=2g/m<2>.24hr. The T is preferably set at 3g/m<2>.24hr in the care of the substrate 2 made of resin. A protective plate 8 is provided via an adhesive agent layer 7 on the inorg. protective layer 6 and the coating layer 9 consisting of the same material as the material of the layer 6 is preferably disposed on the rear faces and side faces of the substrate 2 and the protective plate 8. The medium which has the excellent durability to heat cycles under high humidity and corrosion resistance at and under a high temp. and high humidity is obtd. by such constitution. Such medium is favorably used for recording and reproduction, etc., of information by using heat and light of laser light, etc.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium such as a magneto-optical recording medium that records and reproduces information using heat and light such as laser light.

Prior art and its problems One type of optical recording medium is a medium for magneto-optical memory.

As a recording medium for magneto-optical memory, MnB1. MnAnGe, MnSb.

MnCuB1. GdFe, TbFe.

GdCo, PtCo, TbCo.

TbFeCo, GdFeCo.

TbFeO3, GdIG, GdTbFe.

GdTbFeCoB1. Materials such as CoFe204 are known. These are formed as a thin film on a transparent substrate such as plastic or glass by a method such as a vacuum evaporation method or a sputtering method. Common characteristics of these magneto-optical recording media include the fact that the axis of easy magnetization is perpendicular to the film surface, and that the Kerr effect and Faraday effect are large.

What is required of such a medium is that firstly, the Curie point is around 100 to 200°C and the compensation point is around room temperature, and secondly, defects such as grain boundaries that cause noise are relatively free. Thirdly, a magnetically and mechanically uniform film can be obtained over a relatively large area.

In response to such demands, among the above-mentioned materials, amorphous perpendicular magnetic thin films of rare earth-transition metals have attracted great attention in recent years.

However, in magneto-optical recording media made of such rare earth-transition metal amorphous thin films, if the magnetic thin film layer is stored in contact with the atmosphere, the rare earths may be selectively corroded or oxidized by oxygen and water in the atmosphere. This makes it impossible to record or reproduce information.

Therefore, in general, many studies have been conducted on devices having a structure in which a protective layer is provided on the surface of the magnetic thin film layer on the substrate side or on the surface opposite to the substrate.

Conventionally, protective layers for imparting corrosion resistance such as moisture resistance include - silicon oxide, silicon dioxide, aluminum nitride,
Attempts have been made to provide vacuum-deposited inorganic films such as silicon nitride and zinc sulfide, resin films, etc. (Japanese Patent Application Laid-Open No. 80142/1984). However, none of these is yet satisfactory in terms of corrosion resistance or adhesion between the film and the substrate.

In addition, even when inorganic glass with a certain composition is used for the protective layer, the durability of the medium, especially the prevention of moisture permeation,
It has been disclosed that there is an improvement in adhesiveness (Japanese Unexamined Patent Publications No. 59-52443, No. 60-177).
Publication No. 449).

However, there are strict demands on the durability and corrosion resistance of magneto-optical recording media, and even with these, the effects are still not sufficient, and further improvements are desired.

Note that such a problem also occurs in optical recording media having a so-called phase transition type recording layer.

■Object of the Invention An object of the present invention is to provide an optical recording medium in which deterioration of the recording layer is prevented and excellent corrosion resistance and durability are achieved.

■Disclosure of invention Such objects are achieved by the present invention as described below.

That is, in the present invention, a first inorganic protective layer, a recording layer, and a second inorganic protective layer are sequentially laminated on a substrate to form a laminate, and an organic protective coating layer is provided so as to completely cover this laminate. 40" of a second inorganic protective layer, the optical recording medium comprising:
Moisture permeation amount (JIS Z 0208) in C is 2
The optical recording medium is characterized in that g/rn' -24 hrs or less.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

FIG. 1 shows a magneto-optical recording medium as an embodiment of the optical recording medium of the present invention.

The magneto-optical recording medium 1 is a laminate in which a first inorganic protective layer 3, a magnetic thin film layer 4 as a recording layer, and a second inorganic protective layer 5 are sequentially laminated on a resin substrate 2. , an organic protective coating layer 6 is formed so as to completely cover the top surface, sides, and surfaces of this laminate.

In the present invention, the second inorganic protective layer 5 conforms to JISZ 02
The amount of water permeation (hereinafter referred to as T) at 40°C based on 2008 is set to be 2 g/ml·24 hrs or less.

When T exceeds 2 g/rn'·24 hrs, prevention of moisture permeation is insufficient and corrosion resistance becomes a problem.

The thickness of such second inorganic protective layer 5 is preferably 3
00 to 3000 people, more preferably 500 to 1500 people.

If the thickness is less than 300 people, it will be difficult to achieve the object of the present invention, and if it exceeds 3000 people, there will be problems in terms of economic efficiency.

The material of the second inorganic protective layer 5 exhibiting T as described above may be a compound containing oxygen, carbon, nitrogen, sulfur, etc., such as 5
iOz, Sin, AuN, AIl, 203, Si3N
4. ZnS, B.N.

Various dielectric materials, such as mixtures of the above compounds, including one or more of TiO2, TiN, etc., rare earth metals, etc., and Si, and those containing 0 and N; glasses, such as borosilicate glass, barium borosilicate glass; , aluminum borosilicate glass, or a material containing Si3N4 or the like may be used. Among them, 5
in240-80wt% borosilicate glass, barium borosilicate glass, aluminum borosilicate glass,
It is preferable to substitute a part of these S i O2 with S s 3N <, etc.

Among these, the following are particularly preferred.

(1) 40 to 60 wt% silicon oxide and Bad.

Contains 50 wt% or less of a divalent metal oxide such as Cab, SrO, MgO, ZnO, PbO and/or 10 wt% or less of an alkali metal oxide, and boron oxide and/or aluminum oxide.

(2) Si and other metal or metalloid elements such as Ba and C
a, one or more of Sr, Mg, Zn, Pb, etc., A4. B and at least one of one or more alkali metal elements, the Si atomic ratio in all metals or semimetals is 0.3 to 0.9, and roughly contains 0 and N. , O/(0+N) is 0.4 to 0.8.

On the side opposite to the second inorganic protective layer 5 of the magnetic thin film layer 4, a first
An inorganic protective layer 3 is formed.

When the substrate 2 is made of resin, T of the first inorganic protective layer 3 is preferably 3 g/rn2·24 hrs or less.

When T exceeds 3 g/rrf -24 hrs, prevention of moisture permeation is insufficient and corrosion resistance becomes a problem.

The thickness of this first inorganic protective layer 3 is preferably 200 to
The number of participants is 3,000, preferably 500 to 1,500.

If the thickness is less than 200 people, it will be difficult to achieve the object of the present invention, and if it exceeds 3000 people, there will be problems in terms of economic efficiency.

The material of the first inorganic protective layer 3 may be the same as the first inorganic protective layer described above, but in particular, the first inorganic protective layer 3 may be made of the above-mentioned (1), 300 to 1000 as the base protective layer using the glass layer represented by (2)
5i02.5iO1Si3N
4. 500~1 as a dielectric layer using a dielectric material such as AIN, An203, ZnS, etc., or a mixture thereof.
It is preferable to set up a number of layers for about 500 people.

In this case, the dielectric layer has a refractive index of 1.0 at 800 nm.
8 to 3.0 is preferable, and one containing Si, a rare earth metal and/or A1, and containing O and N is preferable.

These first and second protective layers can be formed using various vapor phase deposition methods.
For example, it is formed by a sputtering method, a vapor deposition method, an ion blating method, a plasma CVD method, a photo-CVD method, a multi-source sputtering method using a target composed of two or more different compositions, a reactive sputtering method using oxygen, etc. Ru.

Furthermore, Ar, N2, etc. present in the film-forming atmosphere may be included as impurities in the protective layer.

Others: FeO203, CuO1 Cr203. MnO,,Coo,Nip.

As2O3 or the like may be contained in an amount of about i, owt% or less of the total.

In the magnetic thin film layer 4 used as a recording layer in the embodiment of the present invention, information is magnetically recorded by a modulated heat beam or a modulated magnetic field, and the recorded information is reproduced by magneto-optical conversion. It is something to do.

The magnetic thin film layer 4 is made of an alloy of rare earth metals such as Gd and Tb and preferably transition metals such as Fe and CO, and is formed as an amorphous film by sputtering, vapor deposition, or the like.

In this case, the total amount of Fe and co is 65 to 85 at%
It is preferable that

The remainder is substantially rare earth metals, especially Gd and/or
Or Tb.

Suitable examples include TbFeCo, GdFe
Co, GdTbFeCo, etc.

Note that these magnetic thin film layers contain Cr, A11. , Ti, Pt, Si, MOIMn, V,
Ni, Cu, Zn, Ge, Au, etc. may be contained.

In addition, as a rare earth element, Sc in a range of 10 at% or less,
Y, La, Ce, Pr%Nd%Pm.

It may contain Sm, Eu%Dy, Ho, Er, Tm, Yb, Lu, etc.

The thickness of such a magnetic thin film layer is usually 100 to I
There are about oooo people.

Other materials for the recording layer include so-called phase change type materials, such as Te-3e, Te-3e-3n%Te-Ge, Te-
In, Te-3n, Te-Ge-3b-3, Te-Ge
-As-3i, Te-3i, Te-Ge-3i-3b
, Te-Ge-B1. Te-Ge-In-Ga, Te-
3t-Bi-Tit, Te-Ge-B1-In-3,
Te-As-Ge-3b, Te-Ge-3e-3, Te
-Ge-3e, Te-As-Ge -G a , T
e −G e −S −1n , S e −G e
-TI, S e -T e -A s, S e
-G e -T It -3b, 5e-Ge-Bi, 5
e-3 (hereinafter referred to as Japanese Patent Publication No. 54-41902, Patent No. 10)
04835, etc.) T e Ox (Te dispersed in Te oxide described in JP-A-58-54338 and Patent No. 974257)
, Te0X+VoX (Patent No. 974258), Te0X+VoX (Patent No. 974257), and others, Te-Tl1. Te-Tl1-3i, 5e-Z
n-3b, Te-3e-Ga.

Chalcogen-based alloys mainly composed of Te and Se such as TeN, Ge-3n, 5i-Sn, etc., which cause an amorphous-crystalline transition, Ag-Zn, Ag-A1. - Alloys that change color due to changes in crystal structure such as Cu, Cu-Al1゜, etc., In-3b
There are alloys that cause changes in crystal grain size.

Such a recording layer may be formed using a dry coating method such as a vapor deposition method, a sputtering method, an ion blating method, or the like. And the layer thickness is 20 nm ~ 1-
It is considered to be a degree.

The substrate 2 is made of glass or resin, and preferred resin materials include acrylic resin, polycarbonate resin, epoxy resin, and polymethylpentene resin.

Among these resins, polycarbonate resins are preferred in terms of durability, particularly resistance to warping and the like.

The polycarbonate resin in this case may be any of aliphatic polycarbonate, aromatic-aliphatic polycarbonate, and aromatic polycarbonate, but aromatic polycarbonate resin is particularly preferred. Among these, polycarbonate resins made from bisphenol are preferred in terms of melting point, crystallinity, handling, etc. Among them, bisphenol A type polycarbonate resin is most preferably used.

In addition, the number average molecular weight of the polycarbonate resin is 10,
It is preferable that it is about 000 to 15,000.

The T of such a substrate 2 is 3 to 5 g/m2・24hrs
That's about it.

At this time, the thickness of the substrate 2 is approximately 1.2 to 1.5 mm.

The refractive index of such a substrate 2 at 830 nm is usually about 1.55 to 1.59.

Note that since recording is performed through the substrate 2, the transmittance for writing or reading light is set to 86% or more.

Tracking grooves or pits may be formed on the surface of such a disk-shaped substrate on which the magnetic thin film layer is formed.

When a groove is formed, the depth of the groove is about ^/8n,
In particular, the range is λ/6 n to λ/12 n (where n is the refractive index of the substrate). Moreover, the width of the groove is 0.
4-2. It is estimated that there are about 100 people.

Further, address pits may be formed.

Generally, it is preferable to irradiate the write light and the read light from the back side of the substrate, using the magnetic thin film layer located in the recessed part of the groove as a recording track part.

With this configuration, the writing sensitivity and the reading C/N ratio are improved, and the tracking control signal is also increased.

In addition, other shapes of the substrate may be used, such as a tape or a drum.

An organic protective coat layer 6 is provided on the second inorganic protective layer 5 so as to completely cover the top and side surfaces of the laminate.

This organic protective coating layer 6 is for providing corrosion resistance to the top and side surfaces of the laminate.

Conventionally, it has been thought that it is sufficient to provide such an organic protective coat only on the top surface of the laminate, but if no organic protective coat is provided on the inner or outer side surfaces of the laminate, corrosion resistance may be compromised. It is enough.

In such a case, the organic protective coat is preferably provided over a range from about 1 mm or more inside the inner peripheral surface of the laminate to about 1 mm or more outside the outer peripheral surface of the laminate.

As the material for the organic protective coat layer 6, various known organic substances may be used.

More preferably, a radiation-curable compound cured with radiation such as an electron beam or ultraviolet rays is used.

The radiation-curable compounds to be used include acrylic acid, methacrylic acid, and acrylic double bonds such as ester compounds thereof, which have unsaturated double bonds that are sensitive to ionization energy and exhibit radical polymerizability, and diallylphthalate. Examples include monomers, oligomers, and polymers containing or introducing into the molecule groups that can be crosslinked or polymerized and dried by radiation irradiation, such as allylic double bonds, unsaturated double bonds such as maleic acid, and maleic acid derivatives. can.

As a radiation-curable monomer, a compound with a molecular weight of less than 2000 is used, and as an oligomer, a compound with a molecular weight of 2000 to 100 is used.
00 is used.

These include styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol methacrylate, (1), 6-hexane glycol diacrylate, (2), 6-hexane glycol dimethacrylate, etc., and are particularly preferred. Examples include pentaerythritol tetraacrylate (
methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), polyfunctional oligoester acrylate (Aronix M-7100, M-5400, M-5500, M-5700
, M-6250, M-6500, M-8030, M-8
060, M-8100, etc. (Toagosei), urethane elastomers with acrylic modified products of Tuborane 4040), or products with functional groups such as C0OH introduced into these, acrylates of phenol ethylene oxide adducts (
methacrylate), an acrylic group (methacrylic group) or ε in the pentaerythritol condensed ring represented by the general formula below.
-Caprolactone-A compound with an acrylic group, 1) (CH2=CHCOOCH2)3 CCH2
0H (special acrylate A) 2) (CH2=CHCOOCH2)3-CCH2
0H3 (special acrylate B) 3) (CH2=CHC0(OC3H6)n 0
CH2)3-CCH2CH3 (Special acrylate C) (Special acrylate D) (Special acrylate E) CH2CH2C00CH=CH2 (Special acrylate F) Compound where m=1, a=2, b=4 (hereinafter referred to as special pentaerythritol) (referred to as condensate A), m = 1, a = 3, b = 3 compound (hereinafter referred to as special pentaerythritol condensate B), m = 1, a = 6, b =
o compound (hereinafter referred to as special pentaerythritol condensate C
), m=2, a=6, b=o (hereinafter referred to as special pentaerythritol condensate), and special acrylates represented by the general formula below.

8) CH2=CHCOO-(CH2CH20)4
C0CH=CH2 (special acrylate H) CH2CH2C00CH=CH2 (special acrylate I) (special acrylate J) A Niacrylic acid, X: Polyhydric alcohol Y: Polybasic acid (Special acrylate K) 12) A-
(-M-N+-M-An Aniacrylic acid, M: dihydric alcohol N: dibasic acid (special acrylate) In addition, radiation-curable oligomers include polyfunctional oligoester acrylates and urethane represented by the general formula below. Examples include acrylic modified elastomers, and those into which functional groups such as C0OH are introduced.

(In the formula, R,, R2: alkyl, n: integer) Furthermore, a radiation-curable compound obtained by radiation-sensitizing modification of a thermoplastic resin may be used.

Specific examples of such radiation-curable resins include acrylic acid, methacrylic acid, or acrylic double bonds such as ester compounds thereof, and diallylphthalate, which exhibits an unsaturated double bond that has radical polymerizability. It is a thermoplastic resin in which groups that can be crosslinked or polymerized by radiation irradiation, such as allylic double bonds and unsaturated bonds such as maleic acid and maleic acid derivatives, are contained or introduced into the molecule of the thermoplastic resin.

Examples of thermoplastic resins that can be modified into radiation-curable resins include vinyl chloride copolymers, saturated polyvinyl sulfate resins,
Examples include polyvinyl alcohol resins, epoxy resins, phenoxy resins, cellulose derivatives, and the like.

Other resins that can be used for radiation sensitivity modification include polyfunctional polyester resins, polyether ester resins, polyvinylpyrrolidone resins, and derivatives (pvp
Also effective are acrylic resins containing at least one of olefin copolymers), polyamide resins, polyimide resins, phenol resins, spiroacetal resins, hydroxyl group-containing acrylic esters, and methacrylic esters as polymerization components.

The T of the organic protective coating layer 6 made of such a radiation-curable compound is 100 to 5000 g/m2 for 24 hours at a thickness of 5 μs.
rs, and the film thickness is 0.1 to 30 layers, more preferably 1 to 10 layers. This film thickness is 0. If it is less than IIa, a uniform film cannot be formed, the moisture-proofing effect in a humid atmosphere will not be sufficient, and the durability of the magnetic thin film layer 4 will not improve. If it exceeds 30#Ixn, the recording medium may warp or cracks may occur in the protective film due to shrinkage during curing of the resin film, making it unsuitable for practical use.

Such a coating film may usually be formed by combining various known methods such as spinner coating, gravure coating, spray coating, and dipping. The conditions for forming the coating film at this time may be appropriately determined in consideration of the viscosity of the mixture of coating film composition, the intended coating thickness, etc.

In order to cure such a coating film to form a protective layer, the coating film may be irradiated with radiation such as electron beams or ultraviolet rays.

When using an electron beam, the radiation characteristics include acceleration voltage 1
It is convenient to use a radiation accelerator of 00 to 750 KV, preferably 150 to 300 KV, and to irradiate with an absorbed dose of 0.5 to 20 Megarat.

On the other hand, when ultraviolet rays are used, a photopolymerizable sensitizer is usually added to the radiation-curable compound as described above.

The photopolymerization sensitizer may be a conventionally known one, such as benzoin type sensitizers such as benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin, α-chlordeoxybenzoin, benzophenone, acetophenone, bisdialkylaminobenzophenone, etc. Examples include ketones, quinones such as acedraquinone and phenanthraquinone, and sulfides such as benzyl disulfide and tetramethylthiuram monosulfide.
The photopolymerization sensitizer is 0.1 to 10% by weight based on the resin solid content.
A range of is desirable.

In order to cure a coating film containing such a photopolymerizable sensitizer and a radiation-curable compound using ultraviolet rays, various known methods may be used.

For example, an ultraviolet light bulb such as a xenon discharge tube or a hydrogen discharge tube may be used.

Preferably, a protective plate 8 is provided on the organic protective coat layer 6 with an adhesive layer 7 interposed therebetween.

That is, in the case of so-called single-sided recording, in which recording and reproduction are performed only from the back side of the substrate 2 (the side on which the magnetic thin film layer 4 is not provided), it is preferable to use this protection plate 8. - The resin material of the protective plate 8 is not particularly required to have transparency, and may be made of various resins such as polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyvinyl alcohol, methacrylic resin, polyamide, polychloride, etc. Various thermoplastic resins such as vinylidene, polycarbonate, polyacetal, fluororesin, phenolic resin,
urea resin, unsaturated polyester resin, polyurethane,
Various thermoplastic resins such as alkyd resins, melamine resins, epoxy resins, and silicone resins can be used.

In addition, various inorganic materials such as glass and ceramics can be protected by a protective plate 8.
It may also be used as

The shape, dimensions, etc. of this material are substantially the same as those of the substrate 2 described above.

Such a protection plate 8 is adhered via the adhesive layer 7 as described above. The thickness of the adhesive layer is approximately 1 to 100 mm.

On the other hand, instead of using the above protection plate 8, another set of substrates having the above magnetic thin film layer 4, protective layers 3, 5, organic protective coating layer 6, etc. are used, and the inner magnetic thin film layers are placed on the inside to face each other. A so-called double-sided recording type may be used in which the substrates are bonded together using an adhesive layer 7 and writing is performed from the back sides of both substrates. Furthermore, it is preferable to provide a coating layer 9 as various protective films on the back surface (the surface on which the magnetic thin film layer 4 is not provided) or on the back surface and side surfaces of the substrate 2 and the protective plate 8.

The material of the coating layer 9 may be the same as that of the organic protective coat layer 6 described above.

■ Effects of the Invention The optical recording medium of the present invention has a protective layer that exhibits a predetermined amount of moisture permeation on the upper and lower surfaces of the recording layer, particularly the magnetic thin film layer, and is coated so as to completely cover the protective layer and the recording layer. has an organic protective coating layer.

Therefore, the medium of the present invention has excellent durability against beat cycles under high humidity and corrosion resistance under high temperature and high humidity, for example.

(2) Specific Examples of the Invention The present invention will be described in more detail below with reference to Examples.

[Example 1] A base protective layer of borosilicate glass was applied by high-frequency magnetron sputtering (target composition (wt%) (Sin2
:50. O.

B203:45. O, Na2O: 3. O.

x2o: 2.0)) to a thickness of 400 mm, and on top of this, a dielectric layer (Si3N4) was formed to a thickness of 800 mm by high frequency magnetron sputtering.
The inorganic protective layer 3 was made as follows.

The T of this first inorganic protective layer 3 according to JIS Z 0208 was 2.4 g/m'·24 hrs.

On such a first inorganic protective layer 3, 21 at% Tb,
A 68 at % Fe, 7 at % Co, and 4 at % Cr alloy thin film was deposited to a thickness of 800 mm by sputtering to form the magnetic thin film layer 4 .

In addition, the target is Fe target, Tb, Co,
A device with a Cr chip mounted thereon was used.

Furthermore, on this magnetic thin film layer 4, a second inorganic protective layer 5 of borosilicate glass is applied to a thickness of 1 by high frequency magnetron sputtering (the target is the same as the first inorganic protective layer).
000 people were set up. T of this second inorganic protective layer is
It was 1.6 g/m'・24 hrs.

A coating composition containing the following radiation-curable compound is applied so as to completely cover the upper surface of the second inorganic protective layer 5 and the side surfaces of the first inorganic protective layer 3, magnetic thin film layer 4, and second inorganic protective layer 5. The material was applied as an organic protective coating layer 6 using a spinner coat. The organic protective coating layer 6 is applied from a position 2 mm inside the inner peripheral surface of the laminate to a position 2 m outside the outer peripheral surface of the laminate.
The position was set to m.

(Coating Composition) 100 parts by weight of polyfunctional oligoester acrylate 5 parts by weight of photosensitizer After the coating composition was formed, it was crosslinked and cured by irradiation with ultraviolet rays for 15 seconds to obtain a cured film. The film thickness was 5y1n.

A magneto-optical recording medium was obtained as described above.

[Example 2] The magneto-optical process was carried out in the same manner as in Example 1, except that the first inorganic protective layer had a T of 3.0 g/d・24 hrs, a composition of SiO, and a film thickness of 800 mm. A recording medium was produced.

[Comparative Example 1] A magneto-optical recording medium was produced in the same manner as in Example 1 except that the organic protective coating layer 6 was not provided.

[Comparative Example 2] An organic protective coating layer 6 was provided only on the upper surface of the second inorganic protective layer 5 and on the outer peripheral sides of the first inorganic protective layer 3, the magnetic thin film layer 4, and the second inorganic protective layer 5, Otherwise, a magneto-optical recording medium was produced in the same manner as in Example 1.

[Comparative Example 3] An organic protective coating layer 6 was provided only on the upper surface of the second inorganic protective layer 5 and on the outer peripheral sides of the first inorganic protective layer 3, the magnetic thin film layer 4, and the second inorganic protective layer 5, Otherwise, a magneto-optical recording medium was produced in the same manner as in Example 2.

[Comparative Example 4] T of the second inorganic protective layer was 4.8 g/m'・24 hrs
A magneto-optical recording medium was produced in the same manner as in Example 1, except that the composition was SiN and the film thickness was 1000.

[Comparative Example 5] An organic protective coating layer 6 was provided only on the upper surface of the second inorganic protective layer 5 and on the outer peripheral sides of the first inorganic protective layer 3, the magnetic thin film layer 4, and the second inorganic protective layer 5, A magneto-optical recording medium was produced in the same manner as in Comparative Example 4 in other respects.

The following characteristics were measured for the above various magneto-optical recording media.

(1) C/N ratio (deterioration on storage) The initial C/N ratio and the amount of change (deterioration) in the C/N ratio after storage for 500 hours at 80° C. and 80% RH were measured under the following conditions.

Rotation speed 4 m/sec Carrier frequency I MHz resolution
30 KHz recording power (830n
m) 3-6mW reproduction power (830nm)
The pit error rate of the EFM signal was measured at the initial stage of 1 mW (2) pit error rate and after storage for 50 hours at 80° C. and 80% R)I.

The results are shown in Table 1.

Table 1 C/N ratio Bit error rate (d
B) (x 1o-6
) Initial period After storage Initial period After storage Example 1 52 52 3 4
Example 2 50 50 3.5
4.5 Comparative Example 4 52 52 3
150 Note that such an effect is caused by phase transition type Te.
-Ge, TeaX, Te-3e, and other recording layers were similarly realized.

From the above results, the effects of the present invention are clear.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a magneto-optical recording medium, which is an example of the optical recording medium of the present invention. Explanation of symbols 1... Magneto-optical recording medium, 2... Substrate 3... First inorganic protective layer, 4... Magnetic thin film layer, 5... Second inorganic protective layer, 6...・Organic protective coat layer, 7... Adhesive layer, 8... Protective plate 9... Coating layer

Claims (2)

[Claims] (1) A first inorganic protective layer, a recording layer, and a second inorganic protective layer are sequentially laminated on a substrate to form a laminate, and an organic protective coat layer is provided to completely cover this laminate. An optical recording medium characterized in that the second inorganic protective layer has a water permeation amount (JIS Z0208) at 40° C. of 2 g/m^2·24 hrs or less. (2) The substrate is made of resin, and the temperature of the first inorganic protective layer is 40°C.
Moisture permeation amount (JISZ0208) is 3g/m^
The optical recording medium according to claim 1, which has a time of 2.24 hrs or less.