JP2523327B2 - Optical recording medium - Google Patents

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.

2. Description of the Related Art As one of optical recording media, there is a medium for a magneto-optical memory.

Materials such as MnBi, MnAlGe, MnSb, MnCuBi, GdFe, TbFe, GdCo, PtCo, TbCo, TbFeCo, GdFeCo, TbFeO ₃ , GdIG, GdTbFe, GdTbFeCoBi, and CoFe ₂ O ₄ are known as recording media for magneto-optical memory. ing. These are formed as thin films on a transparent substrate such as plastic or glass by a method such as a vacuum evaporation method or a sputtering method. The characteristics common to these magneto-optical recording media are that the easy axis of magnetization is perpendicular to the film surface, and that the Kerr effect and the Faraday effect are large.

The requirements for such a medium are firstly that the Curie point is about 100 to 200 ° C. and the compensation point is near room temperature. Secondly, defects such as crystal grain boundaries that cause noise are relatively large. Third, it is possible to obtain a magnetically and mechanically uniform film over a relatively large area.

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

However, in such a magneto-optical recording medium comprising a rare earth-transition metal amorphous thin film, if the magnetic thin film layer is stored in contact with the atmosphere, the rare earth is selectively corroded or oxidized by oxygen or water in the atmosphere. Recording of information,
Reproduction becomes impossible.

Therefore, in general, much research has been conducted on a structure in which a protective layer is provided on the surface of the magnetic thin film layer on the side of the substrate or the side opposite to the substrate.

Conventionally, as a protective layer for imparting corrosion resistance such as moisture resistance, an attempt has been made to provide an inorganic vacuum vapor deposition film or resin film of silicon monoxide, silicon dioxide, aluminum nitride, silicon nitride, zinc oxide or the like ( JP-A-58-80142) is disclosed. However, none of these is still satisfactory in terms of corrosion resistance or adhesion between the film and the substrate.

Further, it is disclosed that even when an inorganic glass having a certain composition is used for the protective layer, the durability of the medium, in particular, prevention of moisture permeation, improvement in adhesiveness and the like are observed (Japanese Patent Application Laid-Open No. 2004-242242). 59-52443 and 60-177449).

Further, JP-A-60-145525 proposes to use a mixed film of Si ₃ N ₄ and SiO ₂ as a protective layer.

However, the requirements for durability and corrosion resistance of the magneto-optical recording medium are strict, and the effect cannot be said to be sufficient with these, and the sensitivity at the time of recording and the C /
The N ratio is not satisfactory either.

Incidentally, such a problem also applies to an optical recording medium having a so-called phase transition type recording layer.

II Object of the invention The purpose of the present invention is to prevent the deterioration of the recording layer, corrosion resistance,
An object of the present invention is to provide an optical recording medium having excellent durability and good recording and reproducing characteristics.

III DISCLOSURE OF THE INVENTION Such an object is achieved by the present invention described below.

That is, in an optical recording medium having a recording layer on a substrate and between the substrate and the recording layer and / or having a protective layer on the recording layer, the protective layer is silicon, aluminum, and boron,
Containing at least one alkaline earth metal element and oxygen, and at least one yttrium and lanthanoid element selected from lanthanum, cerium, praseodymium, neodymium, samarium and europium, yttrium and lanthanoid in the protective layer. The content of at least one element is 3 to 126 at% with respect to the total of silicon, aluminum, boron, and at least one alkaline earth metal element, and silicon, aluminum, boron, and boron in the protective layer are contained. When one or more alkaline earth metal elements are converted into the stoichiometric composition of the oxide of each element, the content of silicon oxide in these oxides is 30 to 70 wt%, Convert one or more of silicon, aluminum, boron and alkaline earth metal elements into the stoichiometric composition of the oxide of each element When an optical recording medium, wherein the content of one or more oxides of alkaline earth metal elements in these oxides is range of 10 to 50 wt%.

IV Specific Configuration of the Invention Hereinafter, the specific configuration of the present invention will be described in detail.

An embodiment of a magneto-optical recording medium of the optical recording media of the present invention is shown in FIG.

In FIG. 1, a magneto-optical recording medium 1 of the present invention has a protective layer 31 on a substrate 2, a magnetic thin film layer 4 as a recording layer on the protective layer 31, and a protective layer 35 on the back surface side of the substrate on the magnetic thin film layer 4. Is provided.

Such a protective layer 31 of the present invention includes silicon, aluminum, boron, at least one of alkaline earth metal elements, oxygen, yttrium and lanthanoid elements.
And more than one seed.

By containing each of these elements, extremely good durability and corrosion resistance are exhibited, and recording and reproducing characteristics are also excellent.

In this case, the effect of the present invention cannot be realized when any one of these essential elements is lacking.

In such a case, one or more of silicon, aluminum, boron and alkaline earth metal (M ² ) is usually contained in the form of oxide to form glass.

With these silicon as glassy material, aluminum,
When boron and one or more kinds of alkaline earth metals (M ² ) are converted into stoichiometric compositions of oxides of the respective elements,
The content of silicon oxide in these oxides is 30 ~ 70wt%
Is.

If this is less than 30 wt%, it is disadvantageous in terms of corrosion resistance,
This is because if it exceeds 70 wt%, it is disadvantageous in terms of stability.

Further, when converted to a stoichiometric composition oxide, the content of one or more oxides of alkaline earth metal (M ² ) in the above oxide is 10 to 50 wt%. This is because if it is less than 10 wt%, it is disadvantageous in terms of corrosion resistance, and if it exceeds 50 wt%, it is disadvantageous in terms of stability.

As alkaline earth metal element (M ² ), Ba, Ca, Mg, Sr
One or more of Ba, Ca, Sr, among others,
It is preferable to use three kinds. When two or more kinds of M ² are used, their respective quantitative ratios are arbitrary.

In addition, at least one of silicon and alkaline earth metal elements M ₂ ,
The stoichiometric compositions of aluminum and boron oxides are SiO ₂ , M ² O, Al ₂ O ₃ and B ₂ O ₃ , respectively.

Further, the glassy composition contains aluminum and boron as described above. The balance of the vitreous composition is formed of an oxide of aluminum and boron, so that the corrosion resistance is further improved.

 The amount ratio of B and Al to each other is arbitrary.

In the above glassy material, each of the above elements is contained as an oxide as described below.

First, Si is usually contained as an oxide of Si (usually SiO ₂ ). Alkaline earth metals are also usually oxides (usually
It is contained as M ² O) of BaO, CaO, MgO and SrO.

Al and B are also normal oxides (usually Al ₂ O ₃ , B ₂ O ₃ )
Contained as. That is, in terms of the stoichiometric composition, in addition to SiO ₂ and M ² O, at least one of Al ₂ O ₃ and B ₂ O ₃ is contained to form a glassy material.

These oxides may deviate from the above stoichiometric composition ratio in the protective layer composition.

In the protective layer of the present invention, the vitreous material contains at least one of yttrium and lanthanoid elements. By containing these, recording sensitivity and C / N
The ratio will be better. In this case, yttrium and lanthanoids are yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm) and europium (Eu).
It is one or more elements selected from the group consisting of. At this time, not only the recording and reproducing characteristics such as recording sensitivity and C / N ratio,
This is because better results can be obtained in terms of durability and corrosion resistance.

One or more of these yttrium and lanthanoid elements (hereinafter these are referred to as R) are mixed and contained in the protective layer with the above-mentioned glassy material, but may be contained in the form of element alone or compound. Good. When it is contained as a compound, it is usually preferable to contain it in the form of an oxide.

In such a case, in order to improve the corrosion resistance and durability as well as the recording and reproducing characteristics, the above R is preferably contained in the form of elemental element or partial oxide. This is because each of these elements acts as an oxygen trap in the protective film and contributes to improvement in corrosion resistance and durability.

The content of one or more of these yttrium and lanthanoid elements is silicon, aluminum, boron,
And 3 to 12 for the total of one or more alkaline earth metals
It is more preferably 3 to 107 at%, more preferably 6 at%. This is 3 at%
If it is less than the above, the effect of the present invention is not obtained, and if it exceeds 126 at%, C
This is because the / N characteristic deteriorates.

The above yttrium and lanthanoid elements are generally stoichiometric oxides of each element (generally Y ₂ O ₃ , La ₂ O ₃
90% oxygen content with respect to R ₂ O ₃ such as ₃ , but Ce is CeO ₂ ).
It is preferably contained as the following simple substance or oxide.

 Such a protective layer is usually in an amorphous state.

The analysis of Si, Al, B, alkaline earth metals, yttrium and lanthanoid elements, and other elements in the protective layer may be performed by Auger, SIMS, ESCA, LAMMA or the like.

Further, such a protective layer is formed by various vapor deposition methods, for example, a sputtering method, a vapor deposition method, an ion plating method, a plasma CVD method, a photo CVD method, and more particularly. In particular, it is preferable to use a sputtering method. In this case, a sputtering method using a target corresponding to a composition to be formed, a multi-source sputtering method using a target having two or more different compositions, or a reactive sputtering method using oxygen, etc. Formed by.

Then, it is particularly preferable to use a two-dimensional sputtering method in which the above glassy material and one or more of yttrium and lanthanoid elements are used as targets.

And the thickness of such protective layer is 300 ~ 3000Å,
Particularly, it is preferable to set it to 500 to 2000Å.

If this value is less than 300Å, the weather resistance is poor and
If it exceeds 0Å, the sensitivity will decrease.

Further, as impurities in the protective layer, Ar, N ₂ or the like existing in the film forming atmosphere may enter.

Others, Fe ₂ O ₃ , CuO, Cr ₂ O ₃ , MnO _x , CoO, NiO, As ₂ O ₃
Etc. may be contained up to about 1.0 wt% of the whole.

The magnetic thin film layer 4 used as the recording layer in the present invention is
Information is recorded magnetically by a modulated heat beam or a modulated magnetic field.
It converts light and reproduces it.

As a material of such a magnetic thin film layer 4, an alloy of a rare earth metal such as Gd and Tb and a transition metal such as Fe and Co is preferably formed as an amorphous film by sputtering, vapor deposition or the like.

In this case, the total content of Fe and Co is preferably 65 to 85 at%.

And the balance is substantially rare earth metals, especially Gd and / or
Or Tb.

And, as a preferable example thereof, TbFeCo, GdFeCo, GdTb
FeCo etc.

In these magnetic thin film layers, C is contained in the range of 10 at% or less.
r, Al, Ti, Pt, Si, Mo, Mn, V, Ni, Cu, Zn, Ge, Au
Etc. may be contained.

In addition, as a rare earth element, Sc, Y, and
La, Ce, Pr, Nd, Pm, Sm, Eu, Dy, Ho, Er, Tm, Yb, Lu
Etc. may be contained.

The thickness of such a magnetic thin film layer is usually 100 to 10000Å
It is a degree.

In addition, as a material of the recording layer, a so-called phase transition type material such as Te-Se, Te-Se-Sn, Te-Ge, Te-Tn, Te-Sn, Te-
Ge-Sb-S, Te-Ge-As-Si, Te-Si, Te-Ge-Si-S
b, Te-Ge-Bi, Te-Ge-In-Ga, Te-Si-Bi-Tl, Te
-Ge-Bi-In-S, Te-As-Ge-Sb, Te-Ge-Se-S,
Te-Ge-Se, Te-As-Ge-Ga, Te-Ge-S-In, Se-Ge
-Tl, Se-Te-As, Se-Ge-Tl-Sb, Se-Ge-Bi, Se-
S (above, Japanese Examined Patent Publication No. 54-41902, Patent No. 1004835, etc.) TeO _x (Te dispersed in the Te oxide described in JP-A No. 58-54338 and Japanese Patent No. 974257), TeO _x + PbO _x ( Patent No. 974258), TeO _x + VO _x (Patent No. 974257), other, Te-Tl, Te
-Tl-Si, Se-Zn-Sb, Te-Se-Ga, TeN _{x and} other Te, Se-based chalcogen-based Ge-Sn, Si-Sn and other amorphous-crystalline transition alloy Ag There are alloys such as —Zn, Ag—Al—Cu, and Cu—Al that change color due to a change in crystal structure, and alloys such as In—Sb that cause a change in crystal grain size.

Such a recording layer may be formed by using a dry coating method such as a vapor deposition method, a sputtering method or an ion plating method. The layer thickness is about 20 nm to 1 μm.

The substrate 2 is made of glass or resin, and preferable resin materials include acrylic resin, polycarbonate resin,
Epoxy resins, polymethylpentene resins and the like can be mentioned.

Among these resins, a polycarbonate resin is preferable in terms of durability, particularly resistance to warping and the like.

In this case, the polycarbonate resin may be any of an aliphatic polycarbonate, an aromatic-aliphatic polycarbonate and an aromatic polycarbonate, but an aromatic polycarbonate resin is particularly preferable. Of these, a polycarbonate resin made of bisphenol is preferable in terms of melting point, crystallinity, handling, and the like. Among them, the bisphenol A type polycarbonate resin is most preferably used.

The number average molecular weight of the polycarbonate resin is 10,0
It is preferably about 00 to 15,000.

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

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

On the magnetic thin film layer formation surface of such a disc-shaped substrate,
A groove for tracking may be formed.

The depth of the groove is about λ / 8n, particularly λ / 6n to λ / 12n (where n is the refractive index of the substrate). The width of the groove is about 0.4 to 2.0 μm.

 Further, a pit for an address may be formed.

Then, it is usually preferable to irradiate the writing light and the reading light from the back surface side of the substrate with the magnetic thin film layer located in the concave portion of the groove as a recording track portion.

With this configuration, the write sensitivity and the read C / N ratio are improved, and the tracking control signal is increased.

Further, other shapes of the substrate may be tapes, drums, and the like.

In the present invention, a protective layer on the back surface side of the substrate is formed on the magnetic thin film layer 4.
35 may be provided.

The material of the substrate backside protective layer 35 is not particularly limited as long as it is made of glass, and the same material as the protective layer 31 may be used.

In this case, as a preferable protective layer material, Japanese Patent Application No. 61-3
00859, 61-302275, 61-303224, 61-307300
No. 61, No. 61-313614, No. 61-313615, No. 61-314949,
Nos. 61-314948 and 61-313720 are disclosed. At this time, the durability and corrosion resistance are more excellent.

Further, the substrate backside protective layer 35 may be made of the same material as the protective layer 31. In some cases, if necessary, the protective layer 31 has a different composition from the above, and only the substrate back surface side protective layer 35 contains the above Si, M ² , Al, B, R, and O. May be

In addition, such a method for forming the substrate back surface side protective layer 35 is
The protective layer 31 may be formed according to the method, and the film thickness is 300.
It is preferably about 3,000 Å, particularly 500 to 2,000 Å.

Further, usually, the organic protective coat layer 5 is provided on the protective layer 35 on the back surface of the substrate.

As the material of the organic protective coat layer 5, generally, various known organic substances may be used.

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

Examples of the radiation-curable compound used include acrylic acid having an unsaturated double bond that is sensitive to ionization energy and exhibits radical polymerizability, methacrylic acid, or an acrylic double bond such as an ester compound thereof, or a diallyl phthalate compound. Examples include monomers, oligomers and polymers having or introduced in the molecule a group that is crosslinked by irradiation with radiation such as allyl double bond, unsaturated double bond such as maleic acid or maleic acid derivative, or polymerized and dried. it can.

A compound having a molecular weight of less than 2000 is used as the radiation-curable monomer, and a compound having a molecular weight of 2000 to 10,000 is used as the oligomer.

These include styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol methacrylate, 1,6-hexane glycol diacrylate, 1,6-hexane glycol dimethacrylate, etc., but especially preferred As, pentaerythritol tetraacrylate (methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), polyfunctional oligoester acrylate (Aronix M-7100, M-5400 , M-55
00, M-5700, M-6250, M-6500, M-8030, M-80
60, M-8100, etc., Toa Gosei), acrylic modified urethane elastomer (Nipporan 4040), or those into which a functional group such as COOH has been introduced, acrylate (methacrylate) of phenol ethylene oxide adduct, the following general A compound having an acrylic group (methacrylic group) or ε-caprolactone-acrylic group on the pentaerythritol condensed ring represented by the formula, _{1) (CH 2 = CHCOOCH 2} ) 3 -CCH 2 OH ( special acrylate _{A) 2) (CH 2 =} CHCOOCH 2) 3 -CCH 2 OH 3 ( special acrylate B) 3) [CH ₂ = CHCO (OC ₃ H ₆ ) _n- OCH ₂ ] _3- CCH ₂ CH ₃ (Special acrylate C) In the formula, a compound of m = 1, a = 2, b = 4 (hereinafter referred to as a special pentaerythritol condensate A), a compound of m = 1, a = 3, b = 3 (hereinafter referred to as a special pentaerythritol condensate B) , M = 1, a = 6, b = 0 compound (hereinafter referred to as special pentaerythritol condensate C), m = 2, a = 6, b = 0 compound (hereinafter referred to as special pentaerythritol condensate D) , And special acrylates represented by the following general formula.

_{8) CH 2 = CHCOO- (CH} 2 CH 2 O) 4 -COCH = CH 2 ( special acrylate H) _{12) AM-N n -M-} A A: acrylate, M: 2 dihydric alcohol N: 2 dibasic acid (special acrylate L) As the radiation-curable oligomer, a polyfunctional oligoester acrylate represented by the following general formula And acrylic modified products of urethane elastomers, and those obtained by introducing a functional group such as COOH into these.

Further, a radiation-curable compound obtained by subjecting a thermoplastic resin to radiation-sensitive modification may be used.

As a specific example of such a radiation curable resin, acrylic acid showing an unsaturated double bond having radical polymerizability,
Groups that crosslink or polymerize upon irradiation, such as acrylic double bonds such as methacrylic acid or their ester compounds, allyl double bonds such as diallyl phthalate, and unsaturated bonds such as maleic acid and maleic acid derivatives. Is contained or introduced in the molecule of the thermoplastic resin.

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

Other resins that can be used for radiation-sensitive modification include polyfunctional polyester resins, polyetherester resins, polyvinylpyrrolidone resins and derivatives (PVP
Olefin copolymers), polyamide resins, polyimide resins, phenol resins, spiro acetal resins, acrylic resins containing at least one hydroxyl group-containing acrylic ester and methacrylic ester as a polymerization component are also effective.

Organic protective coat layer 5 of such a radiation-curable compound
Has a thickness of 0.1 to 30 μm, more preferably 1 to 10 μm.

If this film thickness is less than 0.1 μm, a uniform film cannot be formed, and the moisture-proof effect in an atmosphere with high humidity is insufficient,
The durability of the magnetic thin film layer 4 is not improved. If it exceeds 30 μm, warpage of the recording medium or cracks in the protective film may occur due to shrinkage during curing of the resin film, which is not practical.

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

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

When using an electron beam, the radiation characteristics are acceleration voltage
It is expedient to use a radiation accelerator of 100 to 750 KV, preferably 150 to 300 KV, and to irradiate it with an absorbed dose of 0.5 to 20 megarads.

On the other hand, when ultraviolet rays are used, a photopolymerization sensitizer is usually added to the above-mentioned radiation-curable compounds.

The photopolymerization sensitizer may be a conventionally known one,
For example, benzoin based compounds such as benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin, α-chlordeoxybenzoin, ketones such as benzophenone, acetophenone and bisdialkylaminobenzophenone, quinones such as anthraquinone and phenanthraquinone, and benzyl disulfide And sulfides such as tetramethylthiuram monosulfide.
The photopolymerization sensitizer is preferably in the range of 0.1 to 10% by weight based on the resin solid content.

Then, in order to cure the coating film containing such a photopolymerization sensitizer and the radiation-curable compound by ultraviolet rays, various known methods may be used.

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

A protective plate 7 is usually provided on the organic protective coat layer 5 with an adhesive layer 6 interposed therebetween.

That is, the protective plate 7 is used in the case of so-called single-sided recording in which recording / reproduction is performed only from the back surface (surface on the side where the magnetic thin film layer 4 is not provided) of the substrate 2.

The resin material of the protective plate 7 is not particularly required to have transparency, and various resins such as polyethylene, polyvinyl chloride, polystyrene, polypropylene,
Polyvinyl alcohol, methacrylic resin, polyamide,
Various types of thermoplastic resin such as polyvinylidene chloride, polycarbonate, polyacetal, fluororesin, phenol resin, urea resin, unsaturated polyester resin, polyurethane, alkyd resin, melamine resin, epoxy resin, silicon resin, etc. are used. It is possible.

Note that various inorganic materials such as glass and ceramic may be used as the protective plate 7.

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

Such a protective plate 7 is bonded via the adhesive layer 6 as described above. The adhesive layer is usually an adhesive such as a hot melt resin and has a film thickness of about 1 to 100 μm.

On the other hand, instead of using the protective plate 7, one set of substrates having the magnetic thin film layer 4, the protective layer 31, the substrate back surface protective layer 35, the organic protective coat layer 5 and the like is further used to set both magnetic thin film layers. It may be a so-called double-sided recording type in which they are opposed to each other with the inner side facing each other and they are bonded together by using the adhesive layer 6, and writing is performed from the back surface side of both substrates. Further, it is preferable that the back surface of the substrate 2 or the protective plate 7 (the surface on the side where the magnetic thin film layer 4 is not provided) is coated with various protective films.

The material of the coating may be the same as the material of the organic protective coating layer 5 described above.

V. Effect of the Invention The optical recording medium of the present invention has extremely good recording and reproducing characteristics such as recording sensitivity and C / N ratio, and durability,
Corrosion resistance is also very good.

VI Specific Examples of the Invention Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention.

Example 1 On a substrate 2 of bisphenol A-based optical disc grade polycarbonate resin having a diameter of 13 cm and a thickness of 1.2 mm, a glassy protective layer 31 having various compositions shown in Table 1 below was provided. In addition, at the time of layer formation, reactive multi-source sputtering was performed in an atmosphere containing oxygen using a predetermined glass and one or more of yttrium and lanthanoid elements as targets.

The wt% in Table 1 was obtained by analyzing the metal element in the protective layer by Auger spectroscopy and converting each element into a stoichiometric composition oxide to determine its content. The stoichiometric composition oxide content of each element is shown in Table 1 as wt% in the stoichiometric composition oxide other than yttrium and the lanthanoid element (R).

In the table, M is Si, alkaline earth metal elements M ² , Al, B
In Table 1, at% of one or more yttrium and lanthanoid elements (R) with respect to M in the film is also shown. The film thickness was 800 Å for each sample.

25at% Tb, 63at% Fe, 7at% Co,
800 Å thickness of 5at% Ti alloy thin film by sputtering
To form a magnetic thin film layer 4.

The target used was an Fe target on which Tb, Co, and Ti chips were placed.

On top of this magnetic thin film layer 4, No. 8 shown in Table 1 is further added.
Of the composition of the protective layer 31 in the substrate back side protective layer 35 to 800 Å
Was set up.

A coating composition containing the following radiation-curable compound was used as the organic protective coating layer 5 on the back surface protective layer 35 of the substrate,
It was formed by spin coating.

(Coating composition) Polyfunctional oligoester acrylate 100 parts by weight Photosensitizer 5 parts by weight After applying such a coating composition, it was irradiated with ultraviolet rays for 15 seconds to be crosslinked and cured to obtain a cured film.

In this way, various samples as shown in Table 1 below were prepared.

 The following characteristics were measured for this.

(1) Durability Heat cycle test ... IEC-2-38 (-10 ℃ -60
C, 90% RH) The time during which the burst error doubled in the above acceleration test was measured. Under this condition, mainly the peeling and cracking of the film contributed to the increase of the burst error.

(2) Corrosion resistance High-temperature, high-humidity (80 ° C., 80% RH) storage test The time during which the burst error doubled in the accelerated test was measured. Under these conditions, the occurrence of pitting (pinhole) mainly contributed to the increase in burst error.

(3) C / N ratio The C / N ratio was measured under the following conditions.

Linear velocity 4m / Sec Carrier frequency 1.0MHz Resolution 30KHz Video bandwidth 100Hz Recording power (830nm) 3-6mW Reproducing power (830nm) 1mw The results are shown in Tables 1 and 2.

It should be noted that such effects are caused by Sr, Mg or La, Ce, Pr, Nd.
But realized equally. In addition, phase transition type Te-Ge, TeO _x ,
The same was realized with a recording layer such as Te-Se.

 From the above results, the effect of the present invention is clear.

[Brief description of drawings]

FIG. 1 is a sectional view of a magneto-optical recording medium showing an example of the present invention. Explanation of symbols 1 ... Magneto-optical recording medium, 2 ... Substrate, 31 ... Protective layer, 35
...... Protective layer on back side of substrate, 4 ... Magnetic thin film layer, 5 ... Organic protective coat layer, 6 ... Adhesive layer, 7 ... Protection plate

Front page continuation (72) Inventor Masaru Takayama 1-13-1, Nihonbashi, Chuo-ku, Tokyo TDK Corporation (56) Reference JP-A-63-317941 (JP, A) JP-A-63-317942 ( JP, A) JP 58-100250 (JP, A) JP 56-130394 (JP, A)

Claims (4)

(57) [Claims] 1. An optical recording medium having a recording layer on a substrate and a protective layer between the substrate and the recording layer and / or on the recording layer, wherein the protective layer is silicon, aluminum and boron. Containing at least one alkaline earth metal element and oxygen and at least one lanthanoid element selected from yttrium and lanthanum, cerium, praseodymium, neodymium, samarium and europium, and yttrium and The content of one or more lanthanoid elements is 3 with respect to the total of silicon, aluminum, boron, and one or more alkaline earth metal elements.
Content of ˜126 at%, and when one or more of silicon, aluminum, boron and alkaline earth metal elements in the protective layer are converted into stoichiometric composition of oxide of each element, oxidation in these oxides When the content of silicon is 30 to 70 wt%, and when one or more of silicon, aluminum, boron and alkaline earth metal elements in the protective layer are converted into the stoichiometric composition of the oxide of each element, The content of one or more oxides of alkaline earth metal elements in these oxides is
An optical recording medium characterized by being 10 to 50 wt%. 2. A protective layer is provided between the substrate and the recording layer, and the protective layer comprises silicon, at least one of alkaline earth metal elements, aluminum, boron, oxygen, yttrium and lanthanoid elements. The optical recording medium according to claim 1, containing one or more of 3. A protective layer is provided between the substrate and the recording layer and on the recording layer, and the protective layer at least between the substrate and the recording layer is silicon and at least one kind of alkaline earth metal element. The optical recording medium according to claim 1, which contains aluminum, boron, oxygen, and one or more of yttrium and lanthanoid elements. 4. The optical recording medium according to any one of claims 1 to 3, wherein the protective layer has a thickness of 300 to 3000Å.