JPH04328345A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain the recording medium which has excellent long-term reliability and oxidation resistance, high C/N, wide recording power margin, and low dependency of a recording sensitivity on a line speed by specifying film constitution and film compsn. CONSTITUTION:This magneto-optical recording medium 1 is constituted by laminating a 1st protective film 3, a magneto-optical recording film 4, a 2nd protective film 5, a metallic film 6, and an over coat film 7 in this order on a substrate 2. For example, silicon nitride films are used for the protective films 3, 5. The magneto-optical recording film 4 is constituted of an amorphous alloy film which consists of at least one kind of the elements selected from at least one kind selected from (i) 3d transition metals, (ii) corrosion resistant metals and (iii) rare earth elements, is specified in the content of the above- mentioned corrosion resistant metals to 5 to 30 atomic % and has the axis of easy magnetization perpendicular to the film plane. The metallic film 6 consists of an aluminum alloy, for which an Al-Cr alloy, Al-Cu alloy, etc., are used.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD OF THE INVENTION The present invention relates to a magneto-optical recording medium that has excellent long-term reliability, oxidation resistance, and magneto-optical recording characteristics, and more specifically, the present invention relates to a magneto-optical recording medium that has excellent long-term reliability and oxidation resistance, and has low recording power. The present invention relates to a magneto-optical recording medium having excellent magneto-optical recording characteristics such as a wide margin, low dependence of recording sensitivity on linear velocity, and high C/N ratio.

0002

[Technical background of the invention] Transition metals such as iron and cobalt,
A magneto-optical recording film made of an alloy with rare earth elements such as terbium (Tb) and cadrinium (Gd) has an axis of easy magnetization perpendicular to the film surface, and this entire surface is magnetized in one direction. It is known that it is possible to form small reversed magnetic domains that are oriented in the opposite direction to the magnetization direction. By associating the presence or absence of this inverted magnetic domain with "1" and "0", it becomes possible to record digital signals on the magneto-optical recording film as described above.

Magneto-optical recording films made of such transition metals and rare earth elements are known, for example, from Japanese Patent Publication No. 57-206
No. 91 discloses Tb-Fe containing 15 to 30 atom % of Tb.
A magneto-optical recording film is disclosed. Also, a magneto-optical recording film made of Tb-Fe added with a third metal is also used. Furthermore, magneto-optical recording films such as Tb--Co and Tb--Fe--Co are also known.

[0004] Various methods have been attempted to add a third metal to such Tb-Fe based, Tb-Co based, etc. magneto-optical recording films in order to improve the oxidation resistance of these thin films. .

It is desired that a magneto-optical recording medium formed by laminating such a magneto-optical recording film on a substrate has excellent long-term reliability and is unlikely to cause reading errors even after long-term use.

It has also been desired that a magneto-optical recording medium formed by laminating such a magneto-optical recording film on a substrate has improved recording sensitivity. Furthermore, when writing information on such a magneto-optical recording medium, it is desired that the recording power margin be wide and that the dependence of recording sensitivity on linear velocity be small. A wide recording power margin when writing information means that when information is written to a magneto-optical recording medium using a laser beam, etc., even if the power of the laser beam used as the writing light changes slightly, the magneto-optical It means that information can be written on a recording medium, and the linear velocity dependence of recording sensitivity is small.When information is written to a magneto-optical recording medium using a laser beam, etc., the linear velocity changes at the recording position. However, this means that the optimum recording power of the laser beam used as the writing light changes only in a small way. In this way, reading errors are less likely to occur even after long-term use, and it has excellent long-term reliability and oxidation resistance.In addition, it has a high C/N ratio, a wide recording power margin, and a line of recording sensitivity. It is desired that a magneto-optical recording medium with low speed dependence be developed.

[0007] The inventors of the present invention made extensive studies to obtain the above-mentioned magneto-optical recording medium, and found that a specific first protective film, a specific magneto-optical recording film, and a specific second protective film were formed on the substrate. The present invention was completed by discovering that a magneto-optical recording medium formed by laminating a film, a specific metal film, and an overcoat film in this order has excellent properties.

[0008]

OBJECTS OF THE INVENTION The present invention aims to solve the problems associated with the prior art as described above.
It also has excellent oxidation resistance, does not deteriorate magneto-optical recording characteristics even after long-term use, has a high C/N ratio, has a wide recording power margin, and has low linear velocity dependence of recording sensitivity. The purpose is to provide a small magneto-optical recording medium.

[0009]

SUMMARY OF THE INVENTION A magneto-optical recording medium according to the present invention includes a first protective film (first enhancement film), a magneto-optical recording film,
A magneto-optical recording medium in which a second protective film (second enhancement film), a metal film, and an overcoat film are laminated in this order, the first protective film (first enhancement film) and the second
The protective film (second enhancement film) is made of SiNx, and the magneto-optical recording film is selected from (i) at least one selected from 3D transition metals, (ii) corrosion-resistant metals, and (iii) rare earth metals. an amorphous alloy thin film having an axis of easy magnetization perpendicular to the film surface, the content of the corrosion-resistant metal being 5 to 30 at%;
It is characterized in that the metal film is made of an aluminum alloy.

Since the magneto-optical recording medium according to the present invention has the above-described film structure and film composition,
It has excellent long-term reliability and oxidation resistance, does not deteriorate recording characteristics even after long-term use, has a high C/N ratio, has a wide recording power margin, and has recording sensitivity that depends on linear velocity. gender is small.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The magneto-optical recording medium according to the present invention will be specifically described below. FIG. 1 is a schematic cross-sectional view of a magneto-optical recording medium according to an embodiment of the present invention.

The magneto-optical recording medium 1 according to the present invention has a substrate 2
On top, a first protective film 3, a magneto-optical recording film 4, a second protective film 5,
The metal film 6 and the overcoat film 7 are laminated in this order.

Substrate The substrate 2 is preferably a transparent substrate, and specifically, in addition to inorganic materials such as glass or aluminum, polymethyl methacrylate, polycarbonate, a polymer alloy of polycarbonate and polystyrene, and US Pat.
Organic materials such as amorphous polyolefins, poly4-methyl-1-pentene, epoxy resins, polyethersulfones, polysulfones, polyetherimides, and ethylene-tetracyclododecene copolymers as shown in No. 614778 can be used. In particular, the above U.S. Patent No. 4
Amorphous polyolefins such as those shown in US Pat. No. 6,147,78 are preferred.

In the present invention, the following substrates are particularly preferably used from the viewpoint of excellent adhesion with the protective film, low birefringence, and ability to protect the recording film from oxidation.

A preferred substrate 2 comprises (a) ethylene;
b) The following formula [I] or [II]

[0016]

[Chemical formula 1]

... [I] (wherein n is 0 or 1,
m is 0 or a positive integer, q is 0 or 1,
R1 to R18 are each independently a hydrogen atom, a halogen atom, or a hydrocarbon group, and R15 to R18 and Ra, Rb may be bonded to each other to form a monocyclic or polycyclic ring; The ring or polycyclic ring may have a double bond, and R15 and R16 or R17 and R18 may form an achilidene group. )

[0018]

[Case 2]

... [II] [wherein p is 0 or an integer of 1 or more, q and r are 0, 1 or 2, and R
1 to R15 are each independently a hydrogen atom, a halogen atom, an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or an alkoxy group, and R5 (or R6) and R9 (or R7) are hydrogen atoms having 1 to 3 carbon atoms. They may be bonded via an alkylene group, or may be bonded directly without any group. ] A copolymer with at least one cyclic olefin selected from the group consisting of unsaturated monomers represented by /g of a cyclic olefin random copolymer.

In the above formula [I], when q is 0, the ring represented by q forms a five-membered ring, and in this case, the cyclic olefin is represented by the following formula.

[0021]

[Chemical formula 3]

(where n is 0 or 1, m is 0 or a positive integer, and R1 to R18 are each independently selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group) Represents an atom or group, R15 to R1
8 may form a monocyclic or polycyclic ring bonded to each other, and the monocyclic ring or polycyclic ring may have a double bond, and R15 and R16, or R17 and R1
8 may form an alkylidene group).

Among such cyclic olefin random copolymers, cyclic olefin random copolymers (hereinafter referred to as cyclic olefin random copolymers [A]) having a softening temperature (TMA) of 70° C. or higher are preferred. used. This cyclic olefin random copolymer [A] is produced by combining a cyclic olefin represented by the general formula [I] or [II] and ethylene in a hydrocarbon mixed solvent or in a liquid phase consisting of the above cyclic olefin. can be produced by copolymerizing a vanadium compound and an organoaluminum compound soluble in the solvent in the presence of a catalyst.

[0024]

[C4]

[0025]

[C5]

[0026]

[C6]

[0027]

[C7]

[0028]

[Chemical formula 8]

[0029]

[Chemical formula 9]

[0030]

[Chemical formula 10]

[0031]

[Chemical formula 11]

[0032]

[Chemical formula 12]

[0033]

[Chemical formula 13]

[0034]

[Chemical formula 14]

[0035]

[Chemical formula 15]

[0036]

[Chemical formula 16]

[0037]

[Chemical formula 17]

[0038]

[Chemical formula 18]

[0039]

[Chemical formula 19]

[0040]

[C20]

[0041]

[C21]

[0042]

[C22]

[0043]

[C23]

[0044]

[C24]

[0045]

[C25]

The cyclic olefin represented by the above formula [I] can be easily produced by subjecting cyclopentadiene and the corresponding olefin to a Diels-Alder reaction.

This cyclic olefin random copolymer [
A] has ethylene and the above-mentioned cyclic olefin as essential components as described above, but in addition to these two essential components, other copolymerizable components may be used as necessary within a range that does not impair the purpose of the present invention. It may contain unsaturated monomer components. As the unsaturated monomer which may be optionally copolymerized,
Specifically, for example, propylene, 1-
Butene, 4-methyl-1-pentene, 1-hexene,
Examples include α-olefins having 3 to 20 carbon atoms such as 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene.

In the above-mentioned cyclic olefin random copolymer [A], repeating units derived from ethylene (
a) is present in an amount of 40 to 85 mol%, preferably 50 to 75 mol%, and the repeating unit (b) derived from the cyclic olefin is present in an amount of 15 to 60 mol%, preferably 25 to 50 mol%. %, and the repeating units (a) derived from ethylene and the repeating units (b) derived from the cyclic olefin are arranged randomly and substantially linearly. Note that the ethylene composition and cyclic olefin composition were measured by 13C-NMR. The fact that this cyclic olefin random copolymer is substantially linear and does not have a gel-like crosslinked structure can be confirmed by completely dissolving the copolymer in decalin at 135°C.

The intrinsic viscosity [η] of the cyclic olefin random copolymer [A] measured in decalin at 135° C. is 0.05 to 10 dl/g, preferably 0.0
It is in the range of 8 to 5 dl/g.

[0050] Also, cyclic olefin random copolymer [
A] The softening temperature (TMA) measured with a thermal mechanical analyzer is 70°C or higher, preferably 90~
The temperature is preferably 250°C, more preferably 100 to 200°C. The softening temperature (TMA) is the DuPont manufactured by The
The thermal deformation behavior of a 1 mm thick sheet was measured using an rmomechanical analyzer. That is, a quartz needle is placed on the sheet, a load of 49 g is applied,
The temperature was increased at a rate of 5° C./min, and the temperature at which the needle penetrated 0.635 mm was defined as TMA. Further, it is desirable that the glass transition temperature (Tg) of the cyclic olefin random copolymer [A] is usually in the range of 50 to 230°C, preferably 70 to 210°C.

Further, the crystallinity of this cyclic olefin random copolymer [A] measured by X-ray diffraction method is as follows:
0 to 10%, preferably 0 to 7%, particularly preferably 0
It is in the range of ~5%.

In the present invention, the softening temperature (
Cyclic olefin random copolymer [A] having TMA) of 70°C or higher, ethylene and the above formula [I] or [
II] with a cyclic olefin, the intrinsic viscosity [η] measured in decalin at 135°C is in the range of 0.01 to 5 dl/g, and the softening temperature (TMA
) is less than 70°C (hereinafter referred to as cyclic olefin random copolymer [B]). preferable.

[0053] In the cyclic olefin random copolymer [B] having a softening point (TMA) of less than 70°C as described above, the repeating unit (a) derived from ethylene is 60 to
The repeating unit (b) derived from the cyclic olefin is present in an amount of 98 mol%, preferably 60 to 95 mol%, and 2 to 40 mol%, preferably 5 to 40 mol%. The repeating units (a) derived from ethylene and the repeating units (b) derived from the cyclic olefin are arranged randomly and substantially linearly. In addition, the ethylene composition and cyclic olefin composition are 1
Measured by 3C-NMR. The fact that this cyclic olefin random copolymer [B] is substantially linear and does not have a gel-like crosslinked structure can be confirmed by completely dissolving the copolymer in decalin at 135°C.

The intrinsic viscosity [η] of the cyclic olefin random copolymer [B] measured in decalin at 135°C is 0.01 to 5 dl/g, preferably 0.05 to 5 dl/g.
5 dl/g, more preferably in the range of 0.08 to 3 dl/g.

[0055] Also, cyclic olefin random copolymer [
B] has a softening temperature (TMA) measured with a thermal mechanical analyzer of less than 70°C, preferably -10°C.
-60°C, more preferably 10-55°C. Furthermore, the cyclic olefin random copolymer [B]
It is desirable that the glass transition temperature (Tg) of is usually in the range of -30 to 60°C, preferably in the range of -20 to 50°C.

Further, the crystallinity of this cyclic olefin random copolymer [B] measured by X-ray diffraction method is as follows:
0 to 10%, preferably 0 to 7%, particularly preferably 0
It is in the range of ~5%.

In the present invention, when a cyclic olefin random copolymer composition is used as the substrate, the weight ratio of the cyclic olefin random copolymer [A]/the cyclic olefin random copolymer [B] is 100/0.1 to 100/10, preferably 100/0.3 to 1
00/7, particularly preferably 100/0.5 to 10
A range of 0/5 is desirable. By blending component [B] with component [A] within this range, the substrate itself can adhere to the optical recording film used in the present invention under harsh conditions while maintaining its excellent transparency and surface smoothness. It has the effect of further improving the properties compared to the case of only component [A], and [
If the above-mentioned cyclic olefin random copolymer composition made of a blend of [A] and [B] is used as a substrate, excellent adhesion with the protective film used in the present invention can be obtained even after being left under high temperature and high humidity conditions. It has the characteristic of not changing.

The above-mentioned cyclic olefin copolymers [A] and [B] constituting the substrate in the present invention are
-168708 Publication, JP-A-61-120816
No. 61-115912, Japanese Patent Application Laid-Open No. 1983-115912
-115916 Publication, Japanese Patent Application No. 1983-95905, Japanese Patent Application No. 1982-95906, Japanese Patent Application No. 1982-27
It can be manufactured by appropriately selecting conditions according to the method proposed by the applicant in JP-A No. 1308, JP-A No. 61-272216, and the like.

Further, as a resin forming the substrate, a resin of the following formula [III] formed by ring-opening polymerization of a cyclic olefin represented by the above formula [I] together with a cyclic olefin random copolymer as described above may be used. It is also possible to use a polymer or copolymer containing a repeating unit represented by the following formula [IV], which is formed by hydrogenating a repeating unit represented by the above formula [III]. Polymers or copolymers containing these can also be used.

[0060]

[C26]

[0061]...[III]

[0062]

[C27]

...[IV] However, in the above formulas [III] and [IV], m, n, q and R1 to R1
8 and Ra and Rb are m, n, q and R1 in the cyclic olefin represented by the above formula [I]
It has the same meaning as R18 and Ra and Rb.

[0064] Furthermore, the above cyclic olefin copolymer includes:
If necessary, heat stabilizers, weather stabilizers, antistatic agents, slip agents, anti-blocking agents, antifogging agents, lubricants, dyes, pigments, natural oils, synthetic oils, waxes, etc. can be added. The proportions are appropriate amounts. For example, as a stabilizer that may be added as an optional component, specifically, tetrakis[methylene-3(3,5-di-t-butyl-
4-hydroxyphenyl)propionate]methane,
β-(3,5-di-t-butyl-4-hydroxyphenyl)propionic acid alkyl ester (especially carbon number 1
8 or less), phenolic antioxidants such as 2,2′-oxamidobis[ethyl-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate), zinc stearate, calcium stearate , fatty acid metal salts such as calcium 12-hydroxystearate, polyhydric alcohol fatty acids such as glycerin monostearate, glycerin monolaurate, glycerin distearate, pentaerythritol monostearate, pentaerythritol distearate, and pentaerythritol tristearate. Examples include esters. These may be blended alone or in combination; for example, tetrakis[methylene-3(3,5-di-t-butyl-4-
Examples include combinations of hydroxyphenyl)propionate]methane, zinc stearate, and glycerin monostearate.

In the present invention, it is particularly preferable to use a phenolic antioxidant and a fatty acid ester of a polyhydric alcohol in combination, and the fatty acid ester of a polyhydric alcohol is used in combination with one of the alcoholic hydroxyl groups of a trivalent or higher polyhydric alcohol. It is preferable that the polyhydric alcohol fatty acid ester is partially esterified.

Examples of such fatty acid esters of polyhydric alcohols include glycerin monostearate, glycerin monolaurate, glycerin monomyristate, glycerin monopalmitate, glycerin distearate, glycerin dilaurate, etc. fatty acid ester, pentaerythritol monostearate,
Fatty acid esters of pentaerythritol such as pentaerythritol monolaurate, pentaerythritol distearate, pentaerythritol dilaurate, and pentaerythritol tristearate are used.

Such a phenolic antioxidant is used in an amount of 0 to 10 parts by weight, preferably 0.01 to 10 parts by weight, more preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the cyclic olefin random copolymer composition. Part by weight is particularly preferably 0
．． The fatty acid ester of polyhydric alcohol is used in an amount of 0 to 1 part by weight per 100 parts by weight of the composition.
It is used in an amount of 0 parts by weight, preferably 0.01 to 10 parts by weight, more preferably 0.05 to 3 parts by weight.

In addition, the substrate of the magneto-optical recording medium of the present invention may contain silica, diatomaceous earth, alumina, titanium oxide, magnesium oxide, pumice powder, pumice balloon, etc., as long as the object of the present invention and transparency are not impaired. Aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate, dolomite, calcium sulfate, potassium titanate, barium sulfate,
Calcium sulfite, talc, clay, mica, asbestos, glass fiber, glass flakes, glass beads, calcium silicate, montmolinite, bentonite, graphite, aluminum powder, molybdenum sulfide, boron fiber, silicon carbide fiber, polyethylene fiber, polypropylene fiber, polyester Fillers such as fibers and polyamide fibers may also be blended.

In the optical recording medium according to the present invention, the above-mentioned cyclic olefin random copolymer [A
] or the cyclic olefin random copolymer [A] is used, the substrate and the recording layer laminate, especially the protective film, have excellent adhesion, and therefore the recording layer laminate of the present invention has excellent long-term stability and effectively prevents oxidation of the recording film. Therefore, an optical recording film is formed by laminating a first protective film, a recording film, a second protective film, an aluminum alloy film, and an overcoat film on a substrate made of this cyclic olefin random copolymer or a composition containing this copolymer. The media also has excellent durability and long-term stability. Furthermore, the optical recording medium according to the present invention does not suffer from cracks.

[0070] The above-mentioned substrate also has the advantage that warpage under a high humidity atmosphere is relatively small. The thickness of such a substrate 2 is not particularly limited, but is preferably 0.5 to 0.5.
5 mm, particularly preferably 1 to 2 mm.

Protective Film The first protective film 3 and the second protective film 5 used in the magneto-optical recording medium 1 according to the present invention are formed from films having a composition represented by SiNx, and examples of the SiNx film include, for example. Examples include a silicon nitride film or a silicon nitride-containing film.

In the protective film represented by SiNx, it is preferable that 0<x≦5/3, especially 0<x≦4/3 when expressed in atomic ratio. Silicon nitride film such as silicon) or 0<x<4/
A mixed film in which Si3 N4 and Si are mixed so as to have a concentration of 3 is particularly preferably used. Such a protective film made of SiNx can be formed using, for example, Si3 as a target.
A film can be formed by sputtering using N4 or Si3 N4 and Si. Alternatively, the film can be formed by sputtering Si in a nitrogen-containing atmosphere (for example, Ar/N). The first protective film 3 and second protective film 5 made of SiNx are as follows:
Generally, it is desirable to have a refractive index of 1.8 or more, preferably 1.8 to 2.2, and it serves to protect the magneto-optical recording film 4 from oxidation, etc., which will be described later, or to improve the recording properties of the magneto-optical recording film 4. It acts as an enhancing film or both. Also, SiNx (0<x≦4/3)
The first protective film 3 and the second protective film 5 made of the above have particularly excellent crack resistance.

The magneto-optical recording medium of the present invention has a five-layer structure in which a first protective film, a specific magneto-optical recording film, a second protective film, a metal film made of an aluminum alloy, and an overcoat film are laminated on a substrate, Moreover, since SiNx is used as the first protective film and the second protective film, a wide recording power margin can be obtained and linear velocity dependence can be reduced.

In the present invention, the thickness of the first protective film 3 is 4
00 to 2000 angstroms, preferably 700 to 1
500 angstroms, and the film thickness of the second protective film 5 is 50 to 1000 angstroms, preferably 50 to 7 angstroms.
00 angstroms, more preferably 100 to 400 angstroms
It is about angstrom.

In the present invention, by setting the thickness of the protective film within the above range, a magneto-optical recording medium having a good C/N ratio and a wide recording power margin can be obtained.

Further, by setting the thickness of the first protective film within the above range, the apparent θk of the magneto-optical recording medium can be increased. Further, by setting the thickness of the second protective film within the above range, the magneto-optical recording medium can have a wide recording power margin while maintaining an excellent C/N ratio.

Magneto-optical recording film The magneto-optical recording film 4 comprises (i) at least one selected from 3D transition metals, (ii) a corrosion-resistant metal, and (iii)
) At least one element selected from rare earths. (i) 3d transition metals include Fe, Co, Ti, V,
Cr, Mn, Ni, Cu, Zn, etc. are used, and among these, Fe, Co, or both are preferable.

The 3d transition metal is preferably contained in the magneto-optical recording film 4 in an amount of 20 to 90 atomic %, more preferably 30 to 85 atomic %.
It is present in an amount of 35 to 80 atomic %, particularly preferably 35 to 80 atomic %. (ii) By including a corrosion-resistant metal in the magneto-optical recording film 4, the oxidation resistance of the magneto-optical recording film can be improved. Such corrosion-resistant metals include Pt, P
d, Ti, Zr, Ta, Nb, etc., but among these, Pt, Pd, and Ti are preferable, especially Pt or Pd.
Or preferably both.

This corrosion-resistant metal is present in the magneto-optical recording film 4 in an amount of 5 to 30 at%, preferably 5 to 25 at%, particularly 10 to 25 at%, based on the total number of atoms in the recording film. Preferably it is present in an amount of 10 to 20 atom %.

When the corrosion-resistant metal is present in the magneto-optical recording film in the above amount, the oxidation resistance of the resulting magneto-optical recording film is sufficiently improved, and the coercive force Hc changes significantly over time. In this case, the Kerr rotation angle θk does not decrease. In addition, if it is present in an amount exceeding 30 atomic%,
The Curie point of the resulting amorphous alloy thin film tends to be below room temperature.

The magneto-optical recording film 4 has the above (i) and (i)
In addition to i), (iii) it contains at least one element selected from rare earth elements. (iii) Examples of rare earth elements include Gd, Tb
, Dy, Ho, Er, Tm, Yb, Lu, La, Ce,
Examples include Pr, Nd, Pm, Sm, and Eu.

Among these, Gd, Tb, Dy, Ho, Nd,
Sm and Pr are preferably used. At least one rare earth element selected from the above group is contained in the magneto-optical recording film 4, preferably in an amount of 5 to 50 atomic %, more preferably 8
It is present in an amount of from 10 to 40 atom %, particularly preferably from 10 to 40 atom %.

In the present invention, it is particularly preferable that the magneto-optical recording film 4 has a composition as described below. (i) 3d transition element In the present invention, the magneto-optical recording film preferably contains Fe or Co or both as (i) 3d transition element, and Fe and/or Co is 40 atomic % or more. It is desirable that the content is 80 atomic % or less, preferably 40 atomic % or more and less than 75 atomic %, and more preferably 40 atomic % or more and 59 atomic % or less.

Further, Fe and/or Co may be Co/
(Fe+Co) ratio [atomic ratio] is 0 or more and 0.3 or less, preferably 0 or more and 0.2 or less, more preferably 0.01 or more and 0.
．． It is desirable that the amount is 2 or less in the magneto-optical recording film.

[0085] The amount of Fe and/or Co is 40 at%
When the content is in the above range of 80 atomic % or less, there is an advantage that a magneto-optical recording film having excellent oxidation resistance and having an axis of easy magnetization in a direction perpendicular to the film surface can be obtained.

By the way, when Co is added to a magneto-optical recording film, the following phenomena are observed: (a) the Curie point of the magneto-optical recording film increases, and (b) the Kerr rotation angle (θk) increases; As a result, the recording sensitivity of the magneto-optical recording film can be adjusted by adjusting the amount of Co added, and the carrier level of the reproduced signal can be increased by adding Co. In the magneto-optical recording film according to the present invention, the noise level, C
/N ratio, the Co/(Fe+Co) ratio [atomic ratio] is 0.
It is desirable that the range is 0.01 or more and 0.2 or less, preferably 0 or more and 0.2 or less, and more preferably 0.01 or more and 0.2 or less.

The magneto-optical recording film used in the present invention does not undergo any deterioration even after repeated recording and erasing. For example, in the present invention, Pt13Tb2
When a magneto-optical recording film having a composition (atomic %) of 8Fe50Co9 is used, no decrease in the C/N ratio is observed even after 100,000 recording and erasing operations are repeated.

(ii) Corrosion-resistant metal The magneto-optical recording film used in the present invention preferably contains Pt and/or Pd as the (ii) corrosion-resistant metal. is present in the magneto-optical recording film in an amount of 5 to 30 atom %, preferably more than 10 atom % and less than 30 atom %, more preferably more than 10 atom % and less than 20 atom %, and most preferably 11 atom % or more and 1
It is desirable that it is present in an amount of 9 atomic % or less.

Pt and/or Pd in magneto-optical recording film
When the amount of is present in an amount of 5 atomic % or more, especially more than 10 atomic %, the magneto-optical recording film has excellent oxidation resistance, and has the advantage that pitting corrosion does not occur even after long-term use, and the C/N ratio does not deteriorate. has.

For example, Pt13Tb28Fe50Co9
(atomic %) or Pd12Tb28Fe57Co3
The magneto-optical recording medium of the present invention has a magneto-optical recording film having a composition shown in (atomic %) at a relative humidity of 85%, 80%
The C/N ratio does not change at all even if it is kept in an environment of 1,000 hours at ℃.

Furthermore, by adding Pt and/or Pd to the magneto-optical recording film in an amount within the above range, a small bias magnetic field can be applied when recording or reading information to the magneto-optical recording film. A sufficiently high C/N ratio can be obtained. If a sufficiently high C/N ratio can be obtained with a small bias magnetic field, the magnet for generating the bias magnetic field can be made smaller, and heat generation from the magnet can also be suppressed, making it possible to drive optical disks with a magneto-optical recording film. The device can be simplified. Moreover, since a sufficiently large C/N ratio can be obtained with a small bias magnetic field, it becomes easy to design a magnet for magnetic field modulation recording that can be overwritten.

(iii) Rare earth element (RE) The magneto-optical recording film according to the present invention contains a rare earth element (RE), and examples of the rare earth element include Nd, Sm, Pr,
Ce, Eu, Gd, Tb, Dy or Ho is used.

Among these, Nd, Pr, Gd, Tb
, Dy are preferably used, and Tb is particularly preferred. In addition, two or more rare earth elements may be used in combination, and in this case, Tb
It is preferable that the rare earth element contains 50 atomic % or more of the rare earth elements.

[0094] This rare earth element has the advantage of RE/(R
When the E+Fe+Co) ratio [atomic ratio] is expressed as x,
0.15≦x≦0.45 preferably 0.20≦x≦0.
It is desirable that the magneto-optical recording film be present in an amount of 4.

In the present invention, small amounts of various elements may be added to the magneto-optical recording film to improve the Curie temperature, compensation temperature, coercive force Hc, Kerr rotation angle θk, or to reduce costs. These elements can be used in a proportion of, for example, less than 10 atomic % based on the total number of atoms constituting the recording film.

Examples of other elements that can be used in combination include the following elements. (I) 3d transition elements other than Fe and Co, specifically Sc, Ti, V, Cr, Mn, Ni, Cu
, Zn are used.

Among these, Ti, Ni, Cu, Zn, etc. are preferably used. (II) 4d transition elements other than Pd Specifically, Y, Zr, Nb, Mo, Tc, Ru, Rh
, Ag, and Cd are used.

Among these, Zr and Nb are preferably used. (III) 5d transition elements other than Pt Specifically, Hf, Ta, W, Re, Os, Ir, Au
, Hg are used.

Among these, Ta is preferably used. (IV) III Group B element Specifically, B, Al, Ga, In, and Tl are used.

Among these, B, Al, and Ga are preferably used. (V) IVB group element Specifically, C, Si, Ge, Sn, and Pb are used.

Among these, Si, Ge, Sn, and Pb are preferably used. (VI) VB group element Specifically, N, P, As, Sb, and Bi are used.

Among these, Sb is preferably used. (VII) VIB group element Specifically, S, Se, Te, and Po are used.

Among these, Te is preferably used. The magneto-optical recording film 4 having the above composition is an amorphous thin film capable of perpendicular magnetic and magneto-optical recording, which has an axis of easy magnetization perpendicular to the film surface and often exhibits a rectangular loop with good Kerr hysteresis. This can be confirmed by wide-angle X-ray diffraction.

[0104] In this specification, a square loop with good Kerr hysteresis means that the saturated Kerr rotation angle (θk1), which is the Kerr rotation angle at the maximum external magnetic field, and the residual Kerr rotation angle, which is the Kerr rotation angle at zero external magnetic field. Rotation angle (θk
2) means that the ratio θk2 /θk1 is 0.8 or more.

The film thickness of this magneto-optical recording film 4 is 100 to 60
0 angstrom, preferably 100 to 400 angstrom, more preferably about 150 to 350 angstrom.

Metal film In the magneto-optical recording medium 1 according to the present invention, the second metal film as described above is used.
A metal film 6 is provided on the protective film 5.

In the present invention, the metal film 6 is made of an aluminum alloy. This aluminum alloy is composed of aluminum and at least one element other than aluminum.

[0108] Specific examples of the aluminum alloy constituting the metal film 6 include the following. In addition, in the following aluminum alloy, the content of each metal is atomic % with respect to the total number of atoms constituting the aluminum alloy.

[0109] Al-Cr alloy (Cr content 0.1-10
atomic%), Al-Cu alloy (Cu content 0.1 to 10 atomic%), Al-Mn alloy (Mn content 0.1 to 10 atomic%), Al-Hf alloy (Hf content 0.1 to 10 atomic%) 10 atomic%
), Al-Nb alloy (Nb content 0.1-10 at%)
, Al-B alloy (B content 0.1 to 10 at%), Al
-Ti alloy (Ti content 0.1 to 10 at%), Al-
Ti-Nb alloy (Ti content 0.1-5 at%, Nb content 0.1-5 at%), Al-Ti-Hf alloy (Ti
Al-Cr-Hf alloy (Cr content 0.1-5 at%, Hf content 0.1-10 at%) ), Al-Cr-
Ti alloy (Cr content 0.1 to 5 at%, Ti content 0
．． 1-10 at%), Al-Cr-Zr alloy (Cr content 0.1-5 at%, Zr content 0.1-10 at%)
, Al-Ti-Nb alloy (Ti content 0.1 to 5 at%
, Nb content 0.1 to 5 at%), Al-Ni alloy (Nb content 0.1 to 5 at%), Al-Ni alloy (N
i content 0.1 to 10 at%), Al-Mg alloy (Mg
content 0.1 to 10 at%), Al-Mg-Ti alloy (
Mg content 0.1-10 at%, Ti content 0.1-1
0 at%), Al-Mg-Cr alloy (Mg content 0.1
~10 at%, Cr content 0.1~10 at%), Al
-Mg-Hf alloy (Mg content 0.1-10 at%, H
f content 0.1 to 10 at%), Al-Se alloy (Se
Al-Zr alloy (Zr content 0.1-10 at%), Al-Ta alloy (Ta content 0.1-10 at%), Al-Ta-Hf Alloy (Ta
content 0.1-10 at%, Hf content 0.1-10 at%), Al-Si alloy (Si content 0.1-10 at%), Al-Ag alloy (Ag content 0.1 ~10 atomic%
), Al-Pd alloy (Pd content 0.1-10 at%)
, Al-Pt alloy (Pt content 0.1-10 at%).

[0110] Among the aluminum alloys constituting these metal films, the following are particularly preferable because they reduce the linear velocity dependence of the magneto-optical recording medium and have excellent corrosion resistance.

Aluminum alloy containing 0.1 to 10 atomic % of hafnium, aluminum alloy containing 0.1 to 10 atomic % of niobium, 0.5 to 5 atomic % of titanium and 0.5 atomic % of hafnium.
Aluminum alloy containing 5 to 5 atomic % and a total content of titanium and hafnium of 1 to 5.5 atomic %, chromium 0
．． Containing 1 to 5 at% and 0.1 to 9.5 at% of titanium,
Aluminum alloys with a total content of chromium and titanium of 10 atom% or less, containing 0.1 to 10 atom% of magnesium and 0.1 to 10 atom% of chromium, and a total content of magnesium and chromium of 15 atom% or less An aluminum alloy, 0.1-5 atomic percent chromium and 0.1-9.5 atomic percent hafnium
atomic%, with a total content of chromium and hafnium of 10
Aluminum alloy, magnesium 0.
1 to 10 at% and hafnium 0.1 to 10 at%, and the total content of magnesium and hafnium is 15 at%.
Aluminum alloy, chromium 0.1-5 at%
an aluminum alloy containing 0.1 to 9.5 at.% of zirconium and 0.1 to 10 at.% of tantalum and 0.1 to 10 at.% of hafnium, with a total content of chromium and zirconium of 10 at.% or less. Aluminum alloys containing 0.5 to 5 at% of titanium and 0.5 to 5 at% of niobium, with a total content of titanium and niobium of 1 to 5 at.% .5 atomic%
An aluminum alloy containing 0.1 to 10 atomic % of magnesium and 0.1 to 10 atomic % of titanium, the total content of magnesium and titanium being 15 atomic % or less.

[0112] Contains 0.1 to 9.5 atom% of hafnium, 0.1 to 5 atom% of chromium, and 0.1 to 9.5 atom% of titanium, and the total content of hafnium, chromium, and titanium is 1
Aluminum alloy with a content of 0 atomic % or less.

[0113] Aluminum containing 0.1 to 10 atomic % of hafnium, 0.1 to 10 atomic % of magnesium, and 0.1 to 10 atomic % of titanium, and the total content of hafnium, chromium, and magnesium is 15 atomic % or less alloy. Hafnium 0.1-10 atomic%, magnesium 0.1-10
% and 10 atomic % or less of chromium, and the total content of hafnium, magnesium, and chromium is 15 atomic % or less.

[0114] Contains 0.1 to 10 at% of hafnium, 0.1 to 10 at% of magnesium, 0.1 to 10 at% of titanium, and 10 at% or less of chromium, and the total content of hafnium, magnesium, titanium, and chromium. The amount is 15 atomic%
Aluminum alloy that is less than

[0115] Contains 0.1 to 10 at% of titanium, 0.1 to 10 at% of magnesium, and 10 at% or less of chromium, and the total content of titanium, magnesium, and chromium is 1
Aluminum alloy containing 5 atomic % or less.

[0116] Aluminum alloy containing 0.1 to 10 atomic percent of nickel. An aluminum alloy containing 0.1 to 10 at.% of nickel and 2 at.% or less of chromium.

Such a metal film 6 can be formed, for example, on the second protective film by sputtering or the like using a composite target of the above elements or an alloy target thereof.

The metal film 6 as described above may also contain one or more of the following metals (elements) in addition to the metals constituting each metal film 6. Examples of such metals include titanium (Ti), hafnium (Hf), niobium (Nb), chromium (Cr), silicon (Si), tantalum (Ta), copper (Cu), tungsten (W), and dicornium. (Zr), manganese (M
n), magnesium (Mg), vanadium (V), etc., and such other metals are usually contained in an amount of 5 at % or less, preferably 2 at % or less. (However, among the metals (elements) exemplified above, the metal (elements) already contained in the metal film 6 are not added in the above amount. For example,
The aluminum alloy constituting the metal film 6 is the above-mentioned Al
-In the case of Ti alloy, Al-Ti-Hf alloy, etc.
Among the above metals (elements), titanium (Ti) is not further included in the above aluminum alloy in the above amount. ) The film thickness of such a metal film 6 is 100 to 50
00 angstroms, preferably about 500 to 3,000 angstroms, and more preferably about 700 to 2,000 angstroms.

In the present invention, the metal layer made of aluminum alloy functions as a good thermal conductor layer,
It is thought that the presence of this metal layer prevents the center of the pit recorded on the recording layer from becoming excessively hot due to the recording laser beam, and as a result, the linear velocity dependence of the recording power becomes smaller.

[0120] Furthermore, since the metal layer in the present invention has excellent corrosion resistance, it has a characteristic that the linear velocity dependence of the recording medium is small even after long-term use, and it has a protective effect on the recording layer. It is also excellent.

Overcoat Film In the magneto-optical recording medium 1 according to the present invention, an overcoat film 7 is provided on the metal film as described above.

As the overcoat film 7, an ultraviolet curing resin such as an acrylic type ultraviolet curing resin is used. An example of an acrylic type ultraviolet curable resin composition is a composition containing an acrylate oligomer as a main ingredient, to which benzophenone or N,N-dimethyl-4-aminoacetophenone is added as a curing agent of neopentyl glycol diacrylate or trimethylolpropane triacrylate. monomers and acrylic acid ester monomers (CH2=CHCOO
C4 H9, CH2 = CHCOOC6 H13, C
H2=CHCOOC10H21, CH2=CHCO
Examples include a composition obtained by adding benzophenone as a curing agent to a mixture of OC16H33), or A1 or A2 in Table 1 below.

[0123]

[Table 1] In Table 1 above, Celrad 3700: terminal acrylic oligomer, TMPTA: trimethylolpropane triacrylate, and 2-HEA: 2-hydroxyethyl acrylate, respectively.

Such an overcoat film can be formed by applying an ultraviolet curing resin onto a metal film by a coating method such as a roll coating method or a spin coating method.

[0125] The thickness of this overcoat film is 1 to 10
0 μm, preferably 1 to 50 μm. By providing such an overcoat film on the metal film, it is possible to obtain a double-sided recording medium that is unlikely to cause reading errors even after long-term use and has excellent long-term reliability.

[0126] A first protective film as described above, a magneto-optical recording film,
The second protective film and the metal film can be formed on the substrate by conventionally known methods such as sputtering, electron beam evaporation, vacuum evaporation, and ion plating.

[0127]

[Effects of the Invention] The magneto-optical recording medium according to the present invention as described above has a specific film structure and film composition, so it has excellent long-term reliability and oxidation resistance, and retains light even after long-term use. The magnetic recording characteristics do not deteriorate, the C/N ratio is high, the recording power margin is wide, and the linear velocity dependence of recording sensitivity is small. Further, the magneto-optical recording medium according to the present invention has a specific five-layer structure (that is, a structure in which a specific first protective film/specific recording film/specific second protective film/metal film/overcoat film are laminated on a substrate). ), remove the first protective film and the second protective film.
Since SiNx is used as the protective film and an aluminum alloy film is used as the metal film, the recording power margin is wide. Furthermore, since the magneto-optical recording medium according to the present invention has a metal film made of an aluminum alloy, the dependence of recording sensitivity on linear velocity is small.

[0128] In this specification, the optimum recording power refers to the recording power at which the second harmonic of the reproduced signal is minimized with respect to the write signal at f = 1 MHz and a duty of 50%. The smaller the difference in recording power, the smaller the linear velocity dependence.

[0129] The present invention will be explained below with reference to Examples.
The present invention is not limited to these examples. In the following examples, the compositions of the magneto-optical recording film and the metal film are in atomic percent.

[0130]

[Example 1] Ethylene and 1,4,5,8-dimethano-1
,2,3,4,4a,5,8,8a-Amorphous cyclic olefin random copolymer obtained by copolymerizing with octahydronaphthalene (hereinafter abbreviated as DMON)
Ethylene content 59 mol% measured by 3C-NMR analysis,
The DMON content was 41 mol%, the intrinsic viscosity [η] measured in decalin at 135°C was 0.42 dl/g, and the softening temperature (TM
A) Amorphous polyolefin substrate (154°C)
1.2 mm thick) as a first protective film by sputtering using a Si3 N4 target.
A 3N4 film was deposited at a thickness of 1100 angstroms.

[0131] On this Si3 N4 film, a recording film having a composition of Pt10Tb30Fe58Co2 in at. It was deposited with a film thickness of .

[0132] Furthermore, this Pt10Tb30Fe58Co
2. Sputtering Si3N4 as a second protective film onto the film by sputtering using a Si3N4 target.
The film was deposited at a film thickness of 220 angstroms.

[0133] Next, on this Si3N4 film, Al-T
Using an i-Hf composite target, an aluminum alloy film having a composition of Al96Ti2Hf2 in atomic % was deposited to a thickness of 1500 angstroms by sputtering.

[0134] Next, an acrylic ultraviolet curable resin composition (trade name SD101, manufactured by Dainippon Ink and Chemicals Co., Ltd.) was applied onto the metal film using a spin coater, and UV was irradiated.
A magneto-optical recording medium was manufactured by forming an overcoat film with a thickness of 10 μm.

The characteristics of the magneto-optical recording medium thus obtained were measured as follows. Optimum recording power: Recording at a recording frequency of 1 MHz and a duty ratio of 50%, with a reproduction laser power of 1 mW and a linear velocity of 5.
．． 7m/second (second), 11.3m/second (second)
ond) was evaluated.

Power margin: C measured under the following conditions
The range of recording power from the maximum value of /N (C/Nmax) to a decrease of 3 dB was defined as the power margin. That is, in the present invention, the power margin is CNmax -3
This is the range of recording power that can obtain dB or more.

[0137] C/N (dB): Recording frequency 3.7MHz
, Duty ratio 33.3%, reproduction laser power 1.0
It was set as mW. The adhesion between the substrate and the enhancement layer was evaluated as follows.

[0138] Adhesion test [Checkerboard test (JIS K 5
400)]: Cut 11 orthogonal parallel lines on the recording film and enhancement film of the sample using a cutter knife.
Grind at intervals of mm. Make a grid-like cut so that there are 100 squares in 1 cm2.

Peeling was evaluated using cellophane tape (manufactured by Nichiban). Further, the obtained magneto-optical recording medium was left in an atmosphere of 80° C. and relative humidity of 85% for 1000 hours, and then the C/N ratio was measured again.

[0140] The results are shown in Table 2. Further, the bite error rate (BER) of the obtained magneto-optical recording medium was measured after the recording medium was subjected to a heat cycle 20 times in which the temperature was changed from 65°C to -40°C in 24 hours. The bite error rate was 1 x 10-5 initially and 1 x 10-5 after 20 heat cycles.

[0141]

[Example 2] On the same substrate as used in Example 1,
Using a Si3 N4 target, a Si3 N4 film as a first protective film is formed by sputtering to a thickness of 1100 nm.
It was deposited with a film thickness of angstroms.

[0142] On this Si3 N4 film, a recording film having a composition of Pt5 Tb26Fe66Co3 in atomic % of 300 atomic % was formed by sputtering using a composite target consisting of Fe and Co targets with Pt and Tb chips placed on them. It was deposited with a film thickness of angstroms.

[0143] Furthermore, this Pt5 Tb26Fe66Co
3. Sputtering Si3N4 as a second protective film onto the film by sputtering using a Si3N4 target.
The film was deposited at a film thickness of 220 angstroms.

[0144] Next, on this Si3N4 film, Al-T
Using an i-Hf composite target, an aluminum alloy film having a composition of Al96Ti2Hf2 in atomic % was deposited to a thickness of 1000 angstroms by sputtering.

[0145] Next, an acrylic ultraviolet curable resin composition (trade name SD101, manufactured by Dainippon Ink and Chemicals Co., Ltd.) was applied onto the metal film using a spin coater, and UV irradiation was performed.
A magneto-optical recording medium was manufactured by forming an overcoat film with a thickness of 10 μm.

The characteristics of the magneto-optical recording medium thus obtained were measured in the same manner as in Example 1. The results are shown in Table 2.

[0147] The byte error rate (BER) of the obtained magneto-optical recording medium was initially 1 x 10-5,
After 20 heat cycles it was 1 x 10-5.

[0148]

[Example 3] On the same substrate as used in Example 1,
Using a Si3 N4 target, a Si3 N4 film as a first protective film is formed by sputtering to a thickness of 1100 nm.
It was deposited with a film thickness of angstroms.

[0149] On this Si3 N4 film, using a composite target consisting of a target made of Fe and Co and a Tb chip placed on it, T was added in atomic % by a sputtering method.
A recording film having a composition of b25Fe69Co6 was
It was deposited with a film thickness of angstroms.

Further, on this Tb25Fe69Co6 film, a Si3 N4 film as a second protective film was formed by sputtering using a Si3 N4 target.
A film thickness of 0 angstroms was deposited.

[0151] Next, on this Si3N4 film, Al-T
Using an i-Hf composite target, an aluminum alloy film having a composition of Al96Ti2Hf2 in atomic % was deposited to a thickness of 600 angstroms by sputtering.

[0152] Next, an acrylic ultraviolet curing resin composition (trade name SD101, manufactured by Dainippon Ink and Chemicals Co., Ltd.) was applied onto the metal film using a spin coater, and UV irradiation was performed.
A magneto-optical recording medium was manufactured by forming an overcoat film with a thickness of 10 μm.

The characteristics of the magneto-optical recording medium thus obtained were measured in the same manner as in Example 1. The results are shown in Table 2.

[0154] The byte error rate (BER) of the obtained magneto-optical recording medium was initially 1 x 10-5;
After 20 heat cycles it was 1 x 10-5.

[0155]

[Table 2]

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a magneto-optical recording medium according to the present invention.

[Explanation of symbols]

1...Magneto-optical recording medium 2...Substrate 3...First protective film 4...Magneto-optical recording film 5...Second protective film 6...Metal film 7...Overcoat film

Claims (1)

[Claims] 1. A magneto-optical recording medium in which a first protective film, a magneto-optical recording film, a second protective film, a metal film and an overcoat film are laminated in this order on a substrate, wherein the first protective film and the second protective film is made of SiNx, and the magneto-optical recording film is made of (i) at least one kind selected from 3D transition metals, (ii) at least one kind chosen from corrosion-resistant metals, and (iii) rare earth metals. an amorphous alloy thin film having an axis of easy magnetization perpendicular to the film surface, the content of the corrosion-resistant metal being 5 to 30 atomic %, and the metal film being made of an aluminum alloy. A magneto-optical recording medium characterized by: