JP2711532B2 - Optical recording medium - Google Patents

Description

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 for recording and reproducing information using heat and light passing through a laser beam. 2. Related Art and Problems There is a magneto-optical memory medium as one of optical recording media. The recording medium of the magneto-optical memory, MnBi, MnAlGe, MnSb, MnCuBi , GdFe, TbFe, GdCo, PtCo, TbCo, TbFeCo, GbFeCo, TbFeO 3, GdIG, GdTbFe, GdTbFeCoBi, the material such as CoFe ₂ O ₄ is known 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. Characteristics common to these optical recording media are that the magnetic easy axis is perpendicular to the film surface, and that the Kerr effect and the Faraday effect are large. The first requirement for such a medium is that the Curie point is about 100 to 200 ° C. and the compensation point is around room temperature. Second, defects such as crystal grain boundaries that cause noise are relatively low. Third, a magnetically and mechanically uniform film can be obtained over a relatively large area. In response to such demands, among the above materials,
Rare earth-transition metal amorphous perpendicular magnetic thin films have received great attention. However, in such an optical recording medium comprising a rare earth-transition amorphous thin film, if the recording layer is stored in contact with the air, the rare earth is selectively corroded or oxidized by oxygen or water in the air. This makes information recording and reproduction impossible. Further, in order to improve the S / N ratio, it is necessary to increase the rotation angle at the time of reading a record as much as possible. Therefore, in general, many studies have been made on a configuration having an intermediate layer provided on the surface of the recording layer on the substrate side or on the side opposite to the substrate. Conventionally, for imparting corrosion resistance such as moisture resistance, or to increase the rotation angle by adding the effect of multiple interference or the Faraday effect to the Kerr effect, as the intermediate layer, generalized silicon, silicon dioxide, aluminum nitride, It is well known to provide an inorganic vacuum deposited film such as silicon nitride or zinc sulfide or a resin film (Japanese Patent Application Laid-Open Nos. 58-80142 and 59-52443).
No.). However, none of them is still satisfactory in terms of corrosion resistance and the like. Further, as a material of the intermediate layer, a mixture of an oxide and a nitride, particularly a mixture of Si ₃ N ₄ and SiO ₂ , a mixture of Si ₃ N ₄ and SiO, or a mixture of AlM and Al ₂ O ₃ It is also known to use (JP-A-60-145525). However, the corrosion resistance, C / N
It is not satisfactory in terms of ratio, film peeling, cracking, initial deformation of the recording medium such as warpage, film forming speed, and the like. 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 object of the present invention is to prevent the deterioration of the recording layer,
An object of the present invention is to provide a good optical recording medium which has excellent durability and C / N ratio, and has few film peeling, cracks and initial warpage. III Disclosure of the Invention Such an object is achieved by the present invention described below. That is, the present invention relates to an optical recording medium having an intermediate layer on a substrate, a recording layer on the intermediate layer, and a protective layer between the substrate and the intermediate layer and / or on the recording layer. The layer comprises 40-80 wt% silicon nitride;
A light containing 15 to 60% by weight of one or two of aluminum nitride and aluminum oxide, wherein the protective layer is glassy having a composition represented by any of the following (I) to (IV): It is a recording medium. IV Specific Configuration of the Invention Hereinafter, the specific configuration of the present invention will be described in detail. One embodiment of the magneto-optical recording medium of the optical recording medium of the present invention is shown in FIG. In FIG. 1, a magneto-optical recording medium 1 of the present invention has a glassy substrate-side protective layer 31 on a substrate 2, an intermediate layer 4 thereon, and a magnetic layer as a recording layer thereon. A thin film layer 5 is provided. In the present invention, it is preferable to further provide a vitreous substrate backside protective layer 35 on the magnetic thin film layer 5. The intermediate layer 4 used in the present invention contains Si and Al as essential elements. Si and Al are contained as oxides and nitrides, and require silicon nitride as an essential component, and contain one or two kinds of aluminum nitride and aluminum oxide and, if necessary, silicon oxide. At this time, a combination of an oxide and a nitride is preferable. Each of these oxides and nitrides is usually of a stoichiometric composition, but may be of a lesser degree. In this case, the amount of silicon oxide is set to 40 to 80 wt%. If the amount is too large or too small, the recording / reproducing characteristics, durability, and corrosion resistance deteriorate. Incidentally, JP-A-61-22458 and JP-A-61-278.
No. 062 discloses silicon oxide Si ₃ N _{4 of} about 90 to 95 mol% (90
(about wt% or more), and those containing aluminum oxide Al ₂ O ₃ , silicon nitride AlN, etc., are disclosed. However, these are inferior in terms of C / N, durability, etc. It is enough. It is preferable that the content of the oxide and the content of the nitride be rich in the nitride. Usually, the content of the nitrogen is preferably about 1 to 20 times as large as the content of the oxygen. By doing so, a protective layer that maintains excellent recording / reproducing characteristics, is stable, and has excellent durability and corrosion resistance. If it is less than this range, that is, if it is 0 rich, the output will decrease. Conversely, if it is N rich, the film distortion will increase and the durability will decrease. Further, in such an intermediate layer 4, a concentration gradient of a predetermined element may be provided in the thickness direction. In this case, it is preferable to make the substrate side of the intermediate layer 31 rich in N and O. Alternatively, the substrate pattern may be relatively O-rich and the magnetic thin film side may be N-rich. By doing so, a recording medium with little deterioration over time and excellent in recording and reproducing characteristics can be obtained. In a preferred embodiment, when Si and Al are used as the metal or metalloid, their ratio is not particularly limited, but usually, the atomic ratio of Si / Al is about 0.5 to 20. Even if the Si / Al ratio is less than 0.5 or more than 20, excellent durability cannot be obtained. The refractive index of the intermediate layer 4 at a wavelength of 800 nm is as follows:
1.8 to 3.0, more preferably 2.0 to 2.5. When the refractive index is less than 1.8, the Kerr rotation angle amplifying effect is small and the output is reduced. If it exceeds 3.0, the output will decrease and the noise will increase. Such an intermediate layer 4 can be formed by various vapor deposition methods, for example, a sputtering method, a vapor deposition method, an ion plating method, and a plasma method.
It is formed by CVD, light CVD, particularly a multi-source sputtering method using targets of two or more different compositions or a reactive sputtering method using oxygen. And the thickness of such an intermediate layer 4 is 300 to 3000
Å, particularly preferably 700-2000Å. If this value is less than 300 °, the effect of increasing the car rotation angle is small and the weather resistance is poor. If it exceeds 3000 °, the sensitivity is lowered and the production efficiency is lowered. Further, as impurities in the intermediate layer 4, Ar, N _2, or the like existing in the film formation atmosphere may enter. In addition, elements such as Fe, Ni, Cr, Cu, Mn, Mg, Ca, Na, and K can enter as impurities. In the present invention, a glassy substrate-side protective layer 31 is formed on the intermediate layer 4 on the substrate 2 side. Such a substrate-side protective layer 31 is glassy and has any one of the following compositions (I) to (II). (I) A vitreous material containing silicon oxide, aluminum oxide or boron oxide, and an alkali metal oxide, having a silicon oxide content of 40 to 60 wt% and an alkali metal oxide content of 0.5 to 10 wt% What is. (II) a vitreous material containing silicon oxide, aluminum oxide or boron oxide, an alkali metal oxide, and a metal oxide represented by RO (R is a divalent metal element); With an amount of 40-60 wt% and an alkali metal oxide content of 0.5-10 wt%. (III) a vitreous material containing silicon oxide, boron oxide, aluminum oxide, and alkali metal oxide, having a silicon oxide content of 40 to 60 wt% and an alkali metal oxide content of 0.5 to 10 wt% What is. (IV) a vitreous material containing silicon oxide, boron oxide, aluminum oxide, an alkali metal oxide, and a metal oxide represented by RO (R is a divalent metal element); With an amount of 40-60 wt% and an alkali metal oxide content of 0.5-10 wt%. When the above (I) to (IV) are used and the content is within a predetermined range, the durability is remarkably improved. In the compositions (I) to (IV), silicon oxide usually exists in the form of SiO ₂ . Li ₂ O, Na ₂ O, K ₂ O, Rb
₂ O, Cs ₂ O, Fr ₂ O and the like, among them, especially Li ₂ O,
Na ₂ O and K ₂ O are preferred. These are not only one type,
More than one type may be used in combination. Boron oxide and aluminum oxide are usually present in the form of B ₂ O ₃ and Al ₂ O ₃ respectively. The divalent metal oxide represented by RO is BaO, CaO, MgO, Z
nO. These may be used in combination of two or more. Further, regarding the compositions (I) to (IV), in (I), the used boron oxide or aluminum oxide is contained at 30 to 59.5 wt%. In (II), boron oxide or aluminum oxide to be used is contained at 30 to 59.5 wt%, and part or all of the content is replaced with RO metal oxide, and the RO content is 10 to 50 wt% in the whole layer. , Especially 10 to 35 wt%. In (III), boron oxide and aluminum oxide are contained in a total amount of 30 to 59.5 wt%. (III)
In (IV), each content is from 1.0 to 4% of boron oxide.
About 0 wt% and about 3.0 to 45 wt% aluminum oxide. In (IV), the total of boron oxide and aluminum oxide is 10 to 49.5 wt%, and the total of metal oxides represented by RO is 10 to 49.5 wt%.
49.5wt%. The thickness of such a substrate-side protective layer 31 is preferably about 300 to 1000 mm, particularly preferably 400 to 800 mm. The formation of the protective layer 31 is usually performed by various vapor deposition methods as in the case of the intermediate layer 4. Further, instead of such a glassy protective layer, or in addition thereto, a similar material may be provided as a protective layer 35 on the back surface of the substrate on the magnetic thin film layer 5 described later. As in the case of the glassy substrate-side protective layer, the material of the substrate backside protective layer 35 may be appropriately selected and used from the above-mentioned vitreous ones, particularly from the above (I) to (IV). preferable. In this case, the compositions of the protective layer 31 and the protective layer 35 are usually the same as each other, but may be different. The method for forming such a vitreous substrate backside protective layer 35 may be performed according to the method for the protective layer 31 described above. The thickness is preferably about 300 to 3000 mm, particularly preferably 500 to 2000 mm. The magnetic thin film layer 5 used as a recording layer in the present invention is
Information is recorded magnetically by a modulated heat beam or a modulated magnetic field.
The light is converted and reproduced. As a material of such a magnetic thin film layer 5, an alloy of a rare earth metal such as Gd or Tb and preferably a transition metal such as Fe or Co is 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 wt%. The balance is substantially a rare earth metal, particularly Gd and / or
Or Tb. And, as preferable examples thereof, TbFeCo, GdFeCo, GdTb
Co and others. Note that, in these recording layers, Cr, A
l, Ti, Pt, Si, Mo, Mn, V, Ni, Cu, Zn, Ge, Au and the like may be contained. In addition, Sc, Y,
La, Ce, Pr, Nd, Pm, Sm, Eu, Dy, Ho, Er, Tm, Yb, Lu
And the like. The thickness of such a magnetic thin film layer 5 is usually 100 to 10,000.
About Å. 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-In, 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 Patent Publication No. 54-41902, Japanese Patent No. 100004835, etc.) TeO _x (Japanese Patent Application Laid-Open No. 58-54338, Patent No. 974257)
Te dispersed in oxides), 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, Te such TeN _x, chalcogen Ge-Sn mainly composed of Se, Si-Sn and the like of the amorphous - alloy Ag resulting crystalline transition Alloys such as -Zn, Ag-Al-Cu, Cu-Al, which change color due to a change in crystal structure, and alloys, such as In-Sb, which change the crystal grain size, are available. Such a recording layer may be formed using a dry coating method such as an evaporation method, a sputtering method, and an ion plating method. The thickness of the layer is about 20 nm to 1 μm. The substrate 2 used in the present invention is usually made of glass or resin, and is preferably made of acrylic resin,
Polycarbonate resin, epoxy resin, polymethylpentene resin and the like can be mentioned. Among these resins, polycarbonate resins are preferred in terms of durability, particularly resistance to warpage and the like. In this case, the polycarbonate resin may be any of an aliphatic polycarbonate, an aromatic-aliphatic polycarbonate, and an aromatic polycarbonate, and is particularly preferably an aromatic polycarbonate resin. Of these, polycarbonate resins from bisphenol are preferred in terms of melting point, crystallinity, handling, and the like. Among them, 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 a wavelength of 830 nm of such a substrate 2 is usually 1.55 to
It is about 1.59. Since the recording is performed through the substrate 2, the transmittance for writing or reading light is set to 86% or more. A groove for tracking may be formed on the recording layer forming surface of such a disk-shaped substrate. The depth of the groove is about λ / 8n, particularly λ / 6n to λ / 12n (here, the refractive index is based on n). The width of the groove is about 0.4 to 2.0 μm. Further, an address bit may be formed. Usually, it is preferable that the recording layer located in the concave portion of the groove be used as a recording track portion, and that the writing light and the reading light be irradiated from the back side of the substrate. With this configuration, the writing sensitivity and the C / N ratio for reading are improved, and the control signal for tracking is increased. Further, other shapes of the substrate may be tapes, drums, and the like. An organic protective coat layer 6 is provided on the magnetic thin film layer 5 (opposite to the substrate 2) or on the glassy substrate back surface protective layer 35 provided thereon. As the material of the organic protective coating layer 6, various known organic substances may be used. More preferably, a compound obtained by curing a radiation-curable compound with an electron beam or ultraviolet radiation is used. As the radiation-curable compound to be used, an acrylic double bond such as acrylic acid, methacrylic acid, or an ester compound thereof having an unsaturated double bond showing radical polymerizability, adapted to ionization energy, and diallyl phthalate are used. Monomers, oligomers and polymers containing or introducing into the molecule a group capable of crosslinking or polymerizing and drying by irradiation such as an unsaturated double bond such as an allylic double bond, maleic acid and a maleic acid derivative are included. it can. As the radiation-curable monomer, a compound having a molecular weight of less than 2,000 is used, and as the oligomer, one having a molecular weight of 2,000 to 10,000 is used. These also 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. Examples include pentaerythritol tetraacrylate (methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), and polyfunctional oligoester acrylate (Aronix M-7100, M-5400). , M-
5500, M-5700, M-6250, M-6500, M-8030, M-
8060, M-8100, etc., Toa Gosei), acrylic modified products of urethane elastomer (Nipporan 4040), or those obtained by introducing a functional group such as COOH, acrylate (methacrylate) of phenol ethylene oxide adduct, A compound having an acrylic group (methacrylic group) or an ε-caprolactone-acrylic group on a pentaerythritol condensed ring represented by the formula: _{1) (CH 2 = CHCOOCH 2} ) 3 -OCH 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 special pentaerythritol condensate A), a compound of m = 1, a = 3, b = 3 (hereinafter, special pentaerythritol condensate B) A compound of m = 1, a = 6, b = 0 (hereinafter referred to as special pentaerythritol condensate C), a compound of m = 2, a = 6, b = 0 (hereinafter, 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) Examples of the radiation-curable oligomer include a polyfunctional oligoester acrylate represented by the following general formula, an acrylic modified product of a urethane elastomer, and a product obtained by introducing a functional group such as COOH into these. Further, a radiation-curable compound obtained by radiation-modifying a thermoplastic resin may be used. Specific examples of such a radiation-curable resin include acrylic double bonds having an unsaturated double bond having radical polymerizability, methacrylic acid, acrylic double bonds such as ester compounds thereof, and diallyl phthalate. It is a resin in which a group that crosslinks or polymerizes upon irradiation with radiation, such as a unique allylic double bond or an unsaturated bond such as maleic acid or a maleic acid derivative, is 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 polyester resins,
Examples thereof include a polyvinyl alcohol resin, an epoxy resin, a phenoxy resin, and a cellulose derivative. 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, phenolic resins, and spiroacetals. An acrylic resin containing at least one resin, a hydroxyl group-containing acrylic ester and a methacrylic ester as a polymerization component is also effective. Organic protective coating layer 6 of such a radiation-curable compound
Has a thickness of 0.1 to 30 μm, more preferably 1 to 10 μm. If the thickness is less than 0.1 μm, a uniform film cannot be formed, the moisture-proof effect in a high humidity atmosphere is not sufficient, and the durability of the magnetic thin film layer 5 does not improve. In addition, 30μm
If the thickness exceeds the above range, warpage of the recording medium and cracks in the protective film occur due to shrinkage caused by the curing of the resin film, which is not practical. Such a coating film may be usually provided 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 the coating film composition, the desired thickness of the coating film, and the like. In order to cure such a coating film to form a protective layer, the coating film may be irradiated with radiation such as an electron beam or ultraviolet light. When using an electron beam, radiation characteristics include acceleration voltage
It is convenient to use a radiation accelerator of 100 to 750 KV, preferably 150 to 300 KV, and to irradiate so that the absorbed dose becomes 0.5 to 20 Mrad. On the other hand, when ultraviolet rays are used, a photopolymerization sensitizer is usually added to the radiation-curable compound as described above. As the photopolymerization sensitizer, a conventionally known photosensitizer may be used,
For example, benzoin methyl ether, benzoin ethyl ether, α-methyldenzoin, benzoin such as α-chlordeoxybenzoin, benzophenone, acetophenone, ketones such as bisdialkylaminobenzophenone, acetolaquinone, quinones such as phenanthraquinone, benzyl disulfide, Sulfides such as tetramethylthiuram monosulfide and the like can be mentioned.
The photopolymerization sensitizer is desirably in the range of 0.1 to 10% by weight based on the solid content of the resin. In order to cure the coating film containing the photopolymerization sensitizer and the radiation-curable compound with ultraviolet rays, various known methods may be used. For example, an ultraviolet light bulb such as a xenon discharge tube and a hydrogen discharge tube may be used. On such an organic protective coat layer 6, a protective plate 8 is usually provided via an adhesive layer 7. That is, in the case of so-called single-sided recording, in which recording / reproduction is performed only from the back surface (the surface on which the magnetic thin film layer 5 is not provided) of the substrate 2, the protective plate 8 is used. The resin material of the protective plate 8 is not required to be particularly transparent, and various resins, for example, polyethylene, polyvinyl chloride, polystyrene, polypropylene,
Polyvinyl alcohol, methacrylic resin, polyamide,
Various thermoplastic resins such as polyvinylidene chloride, polycarbonate, polyacetal, fluorine resin, phenol resin, urea resin, unsaturated polyester,
Various thermoplastic resins such as polyurethane, alkyd resin, melamine resin, epoxy resin, and silicon resin can be used. Note that various inorganic materials such as glass and ceramic may be used as the protection plate 8. The shape, dimensions, and the like of this are almost the same as those of the above-described substrate 2. Such a protective plate 8 is bonded via the adhesive layer 7 as described above. The adhesive layer is usually an adhesive such as a hot melt resin and has a thickness of about 1 to 100 μm. On the other hand, instead of using the protective plate 8, the magnetic thin film layer 5, the intermediate layer 4, the protective layers 31 and 35, and the organic protective coat layer 6 are used.
Further, one set of substrates having the same structure is used, the recording layers are opposed to each other with the recording layers facing inward, and the substrates are bonded using the adhesive layer 7.
A so-called double-sided recording type in which writing is performed from the back sides of both substrates may be adopted. Further, it is preferable that the back surfaces of the substrate 2 and the protective plate 8 (the surface on which the magnetic thin film layer 5 is not provided) are coated as various protective films. The material of the coating may be the same as the material of the organic protective coat layer 6 described above. V Effect of the Invention The optical recording medium of the present invention has a protective layer, an intermediate layer having a predetermined composition, a recording layer, and, if necessary, a protective layer. Therefore, the medium having such a configuration has the effects of extremely high corrosion resistance, reproduction output, C / N ratio, and low error rate. 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 A glassy substrate-side protective layer 31 was further formed on a substrate 2 made of bisphenol A-based optical disk grade polycarbonate resin having a diameter of 13 cm and a thickness of 1.2 mm, and an intermediate layer 4 was further formed thereon by a sputtering method. In some cases, the layers were formed by a multi-source sputtering method. The film thickness was 500 ° and 800 °, respectively. The composition of the protective layer 31 and the intermediate layer 4 (the composition ratio is converted into the indicated compound) and the refractive index of the intermediate layer 4 at a wavelength of 800 nm are various as shown in Table 1 below. It was taken. The refractive index was adjusted according to the sputtering conditions (gas pressure and gas composition) in addition to the composition. Further, on the intermediate layer 4, 21 at% Tb, 68 at% Fe, 7 at% Co, 4a
A t% Cr alloy thin film was formed to a thickness of 800 ° by sputtering to form a magnetic thin film layer 5. The target used was an Fe target on which Tb, Co, and Cr chips were mounted. On this magnetic thin film layer 5, a glassy substrate backside protective layer 35 of various compositions was further provided. The composition of the vitreous substrate-side protective layer 35 was the same as that of the vitreous substrate-side protective layer 31 used for the predetermined sample. Further, the film thickness was 800 °. On this protective layer 35, a coating composition containing the following radiation-curable compound was provided as an organic protective coat layer 6 by spinner coating. (Coating composition) Polyfunctional oligoester acrylate 100 parts by weight Photomultiplier 5 parts by weight After forming such a coating composition, ultraviolet rays were irradiated for 15 sec and crosslinked and cured to obtain a cured film. Thus, various samples as shown in Table 1 below were produced. The following properties were measured for these. (1) Initial C / N ratio Linear velocity 4m / sec Carrier frequency 1.0MHz Resolution 30KHz Recording power (830nm) 3-6mW Reproduction power (830nm) 1mW (2) Durability Heat cycle test IEC-2-38 (- 10 ℃ ～ + 65
(° C, 93% RH) The time during which the bit error rate doubled in the above acceleration test was measured. Under these conditions, peeling, cracks, etc. of the film mainly contributed to an increase in the bit error rate. Further, the sample was stored at 60 ° C. and 90% RH for 1,000 hours, and changes in the bit error rate, changes in the appearance such as peeling of the film were measured. The bit error rate was measured by recording an NRZ signal under the above conditions. The initial bit error rate is 3 × 10
^-6 . (3) Corrosion resistance High-temperature, high-humidity (70 ° C., 90% RH) storage test The time during which the bit error rate doubled in the accelerated test was measured. Under this condition, the occurrence of pitting (pinhole) mainly contributed to the increase of the bit error rate. Table 1 shows the results. Note that, instead of the substrate-side protective layer 31 and the intermediate layer 4, the thickness is
A dielectric film having a thickness of 500 mm was provided, and a dielectric film having a thickness of 800 mm was provided in place of the protective layer 35 on the rear surface of the substrate.
Comparative Sample No. 26 was prepared in the same manner as the above sample. The composition of both dielectric films of Comparative Sample No. 26 was: AlN: 4.4% by weight, Si ₃ N ₄ : 60.0% by weight, Al ₂ O ₃ : 22.4% by weight, SiO ₂ : 13.2% by weight. Is within the composition range of the intermediate layer. When a test similar to that of the other samples was performed on Comparative Sample No. 25, the initial C / N ratio was 51 dB.
In the durability test, the time until the bit error rate doubled was 600 hours, the change in bit error rate was 4 × 10 ⁻⁶ , and the change in appearance was “small peeling”. In the corrosion resistance test, the time required for the bit error rate to double was 1000 hours or more. From this result, it is clear that the comparative sample No. 26 is significantly inferior in durability compared to the sample of the present invention. it is obvious. The effects of the present invention are clear from the above results. Note that such an effect is due to the phase transition type of Te-Ge, TeO _x ,
The same was realized with a recording layer such as -Se.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a magneto-optical recording medium showing an example of the optical recording medium of the present invention. DESCRIPTION OF SYMBOLS 1... Magneto-optical recording medium, 2.... Substrate 31... , 7 ... adhesive layer, 8 ... protection plate

Claims (1)

(57) [Claims] An optical recording medium having an intermediate layer on a substrate, a recording layer on the intermediate layer, and a protective layer between the substrate and the intermediate layer and / or on the recording layer, wherein the intermediate layer is 40 to 80 wt. % Silicon nitride and an additional 15%
Optical recording characterized in that the protective layer contains one or two kinds of aluminum nitride and aluminum oxide in an amount of up to 60% by weight, and the protective layer is glassy having a composition represented by any of the following (I) to (IV): Medium. (I) A vitreous material containing silicon oxide, aluminum oxide or boron oxide, and an alkali metal oxide, having a silicon oxide content of 40 to 60 wt% and an aluminum oxide or boron oxide content of 30 to 59.5. wt%, alkali metal oxide content of 0.5 to 10 wt%. (II) containing silicon oxide, aluminum oxide or boron oxide, an alkali metal oxide, and a metal oxide represented by RO (R is a divalent metal element selected from Ba, Ca, Mg and Zn) It has a silicon oxide content of 40 to 60 wt%, an aluminum oxide or boron oxide content of 30 to 59.5 wt%, and an alkali metal oxide content of 0.
5 to 10 wt%, part of the content of aluminum oxide or boron oxide is replaced with RO, and the RO content is 10 to 50 wt%. (III) a vitreous material containing silicon oxide, boron oxide, aluminum oxide, and alkali metal oxide, having a silicon oxide content of 40 to 60 wt%, and a total of aluminum oxide and boron oxide contents. 30-59.5wt%,
Those having an alkali metal oxide content of 0.5 to 10% by weight. (IV) Silicon oxide, boron oxide, aluminum oxide, alkali metal oxide, and metal oxide represented by RO (R is a divalent metal element selected from Ba, Ca, Mg and Zn) Contains glassy material, silicon oxide content is 40-60wt%, total sum of aluminum oxide and boron oxide content is 10-49.5wt%, alkali metal oxide content is 0.5-10wt%, RO content Is 10 to 49.5 wt%. 2. 2. The optical recording medium according to claim 1, wherein said intermediate layer further contains 10 wt% or less of silicon oxide. 3. The refractive index of the intermediate layer at a wavelength of 800 nm is 1.8 to 3.0.
The optical recording medium according to claim 1 or 2, wherein