JPS62234254A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To improve durability and productivity by adhering a protective plate via an adhesive agent layer contg. a compd. curable by UV rays which is cured by UV rays onto the surface of a thin amorphous vertical magnetic film layer consisting of a rare earth-transition metal. CONSTITUTION:A magneto-optical recording medium 1 is formed by adhering a magnetic recording part 10 which is formed by having an intermediate layer 3 on a substrate 2, having the thin amorphous vertical magnetic film layer 4 consisting of the rare earth-transition metal on the intermediate layer 3 and having an inorg. protective layer 5 on the thin magnetic film layer 4 and the protective plate 7 provided in the upper part of the recording part 10 to each other via the adhesive agent layer 6 contg. the compd. curable by UV rays. The adhesive agent compd. durable by UV rays to curing by the UV rays. The deterioration of the thin magnetic film layer 4 by the moisture from the protective plate 7 side is thus prevented and the durability is improved. In addition, the productivity is improved.

Description

Detailed Description of the Invention (1) Background Technical Field of the Invention The present invention relates to a magneto-optical recording medium that records and reproduces information using heat and light such as laser light.

prior art As an optical recording medium for magneto-optical memory, MnB1. MnAffiGe, MnSb.

MnCuB1. GdFe, TbFe.

GdCo, PtCo, TbCo.

TbFeCo, GdFeCo, TbFeO3.

Gd1G, GdTbFe.

GdTbFeCoB1. Materials such as CoFe204 are known. These are formed as thin films on transparent plates such as plastics and glass using methods such as vacuum evaporation and sputtering.The common characteristics of these magneto-optical recording media include: easy magnetization The axis is perpendicular to the membrane surface, and the Kerr effect and Faraday effect are large.

Examples of magneto-optical recording methods that take advantage of this property include the following methods.

First, the entire initial film is magnetized to "0", that is, uniformly (this is called erasing). Next, a laser beam is irradiated onto the part where "1" is to be recorded.

The temperature of the area irradiated with the laser beam increases, and when the temperature approaches the Curie point and further exceeds the Curie point, the coercive force Hc approaches 0. If the laser beam is turned off and the temperature is returned to room temperature, the magnetization will be reversed due to the energy of the demagnetizing field.Furthermore, if the external magnetic field is applied in the opposite direction to the initial direction during laser beam irradiation and the temperature is returned to room temperature, the magnetization will be reversed. Then, a signal that becomes "1" is recorded.

Furthermore, since the initial state of recording is "0", the portions that are not irradiated with the laser beam remain as "0".

Reading of a recorded magneto-optical memory is similarly performed by using a laser beam and by rotating the plane of polarization of the reflected light depending on the direction of magnetization of the laser beam irradiation light, that is, by utilizing the magneto-optic effect.

The following requirements are required for such a medium: First, the temperature of one curie point is about 100 to 200°C, and the compensation point is around room temperature.

Second, defects such as grain boundaries that cause noise are relatively small.

Thirdly, a magnetically and mechanically uniform film can be obtained over a relatively large area without using methods such as high-temperature film formation or long-time open film formation.

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

By the way, there are usually two types of magneto-optical recording media having such a rare earth-transition metal amorphous thin film layer as described below.

That is, one of them is a so-called single-sided recording medium in which the above-mentioned magnetic thin film layer is provided on one substrate and writing and reading are performed from the back side of the substrate.

On the other hand, two sets of media used for this single-sided recording are used,
These magnetic layers are bonded together, facing each other via an adhesive layer, for example, to form a so-called double-sided recording medium.

By the way, in these media, if the magnetic thin film layer is stored in contact with the atmosphere, the rare earth elements will be selectively corroded or oxidized by oxygen and water in the atmosphere, making it impossible to record or reproduce information. Become.

Therefore, in general, many structures have been proposed in which various thin protective layers are provided on the magnetic thin film layer.

+1η In the case of the single-sided recording medium mentioned above, +
For example, 5i02゜S io, S i3 N
4. It is known that an inorganic protective film such as AlI303 or AffiN or an organic resin protective film layer is provided, and a protective plate is further provided on this with an adhesive layer formed by solidifying a hot melt adhesive layer or the like. It is being

However, the materials of the protective layer provided on these magnetic thin film layers do not have sufficient moisture resistance, and are particularly poor in moisture resistance in a high temperature and high humidity atmosphere.

Therefore, the present inventors have proposed a protective layer containing a radiation-curable resin (Japanese Patent Application No. 17916-1982).
No. 4, No. 60-179957, No. 60-186869
No. 60-185090, etc.).

This product has an excellent moisture-proofing effect of 47%, but +irf
In a single-sided recording medium having a protective plate as described above,
After the protective layer is provided, the protective plate must be further bonded via an adhesive layer, which complicates the assembly process.

Therefore, in order to deal with such problems, there is a need for further improvements in the structure of media.

(2) Object of the Invention An object of the present invention is to provide a magneto-optical recording medium which is excellent in durability and storage stability in a high humidity atmosphere, and also has good medium productivity.

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

That is, in the present invention, a magnetic recording part having an amorphous perpendicular magnetic thin film layer of a rare earth-transition metal is formed on a substrate, and the surface of the magnetic recording part on the side of the amorphous perpendicular magnetic thin film layer is hardened by ultraviolet rays. The present invention is a magneto-optical recording medium characterized by having a protective plate adhered via an adhesive layer containing a radiation-curable compound.

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

A magneto-optical recording medium as an embodiment of the present invention is shown in FIG.

The magneto-optical recording medium 1 of the present invention usually has an intermediate layer 3 on a base 2F, an amorphous perpendicular magnetic thin film layer 4 of rare earth-transition metal on this, and an inorganic protective layer 5 on this. A magnetic recording section 10 consisting of a magnetic recording section 41 and a protective plate 7 provided in a portion thereof are bonded to each other via an adhesive layer 6 containing a radiation-curable compound as shown in the figure.

The adhesive layer 6 containing the radiation-curable compound of the present invention is
A coating film containing the following radiation-curable compound is cured with ultraviolet light.

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

As a radiation-curable monomer, a compound with a molecular weight of less than 2,000 is used, and as an oligomer, a compound with a molecular weight of 2,000 to too
oo is used.

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 diacrylate, etc. 5 Particularly preferred ones These include pentaerythritol tetraacrylate (methacrylate), pentaerythritol acrylate (
methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), winter functional oligoester acrylate (Aronix M-7100, M-5400, M-5500, M-5700
, M-6250, M-6500, M-8030, M-8
060, M-8100, UV-349HV, etc., Toagosei; LA-3620 Toyo Ink), acrylic modified products of Tuboran 4040) in urethane elastomers, or products with functional groups such as C0OH introduced into these, phenol ethylene oxide Adduct acrylate (methacrylate), acrylic in the pentaerythritol condensed ring represented by the general formula ``J: (methacrylic group) or ε
-Caprolactone-A compound with an acrylic group, 1) (CH2=CHCOOCH2)3-CCH2
0H (special acrylate A) 2) (CH2=CHCOOCH2)3-CCH2
0H3 (special acrylate B) 3) (CH2=CHC0(OC3Ha)n −
0CH2)3-CCH2CH3 (Special acrylate C) (Special acrylate D) (Special acrylate E) CH2CH2C00CH=CH2 (Special acrylate F) In the formula, a compound where m=1, a=2, b=4 (hereinafter referred to as special pentaerythritol) (referred to as condensate A), m = 1, a = 3, b = 3 compound (hereinafter referred to as special pentaerythritol condensate B), m = 1, a = 6, b =
o compound (hereinafter referred to as special pentaerythritol condensate C
), m=2, a=6, b=o (hereinafter referred to as special pentaerythritol condensate), and special acrylates represented by the general formula below.

8) CH2=CHCOO-(CH2CH20)4-
COCH=CH2 (special acrylate H) CH2CH2C00CH=CH2 (special acrylate ■) (special acrylate J) A Niacrylic acid, X:'n+i Alcohol 2)
A(-M-N+-M-A A Niacrinol, M: dihydric alcohol N: dibasic acid (special acrylate) In addition, as a radiation-curable oligomer, polyfunctional oligoester acrylate represented by the general formula Examples include acrylic modified products of urethane elastomers, and those into which functional groups J and C such as COOH are introduced.

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

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

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

Other resins that can be used for radiation sensitivity modification include polyfunctional polyester resins, polyether ester resins, polyvinylpyrrolidone resins, and derivatives (pvp
Olefin copolymers), polyamide resins, polyimide resins, phenolic resins, spiroacetal resins, acrylic esters and methacrylic esters containing hydroxyl groups! ■Acrylic resins that contain at least one type of synthetic acid component are also active.

In addition to the above-mentioned radiation-curable compound, a photopolymerizable sensitizer is usually added to the ultraviolet-curable adhesive layer 6.

As this photopolymerization sensitizer, conventional ones may be used, such as benzoin series such as benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin, α-chlordeoxybenzoin, and ketones such as benzophenone, acetophenone, and bisdialkylaminobenzophenone. kind,
Examples include quinones such as acedraquinone and phenanthraquinone, and sulfides such as hensyl disulfide and tetramethylthiuram monosulfide. The photopolymerization sensitizer is 0.1 to 10% by weight based on the resin solid content.
A range of is preferred.

Such an adhesive layer 6 may be normally formed by various known methods such as spinner coating and gravure coating.
The conditions for forming the coating film at this time may be appropriately determined in consideration of the viscosity of the polymer in the coating film composition, the condition of the substrate surface, the intended coating thickness, etc.

Also, usually such adhesive application II! Before curing 2 with ultraviolet rays, a transparent protection plate 7, which will be described later, is placed on top of this coating in close contact with it. Then, the coating film is irradiated with ultraviolet rays that pass through the protection plate 7 from above the protection plate 7 to cure the coating film.

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

The ultraviolet irradiation conditions may be those known in the art.

The adhesive layer 6, which is obtained by curing a coating film containing a radiation-curable compound as described above with ultraviolet rays, not only plays the role of adhesion between the magnetic recording section 10 of the medium 1 of the present invention and the protective plate 7, but also It also has the function of a protective film to prevent deterioration of the magnetic thin film layer 4 from moisture etc. from the protective plate 7 side.

Then, the adhesive layer 6 cured by ultraviolet rays of the present invention
The storage stability is greatly improved by using .

Furthermore, by using this material, the protective film and adhesive layer, which were conventionally provided separately, are now combined into one, and productivity is extremely high.

The thickness of the adhesive layer 6 of the present invention is 1 to 100 μm.
, more preferably 10 to 50 μm.

If this value exceeds 100 μI, it takes less time to cure and it is difficult to harden to the inside, and if it is less than 1 μm, it is difficult to apply uniformly and the contact strength decreases.

The protective plate 7 used in the present invention is manufactured by transmitting ultraviolet rays into the protective plate 7 when assembling the medium 1 as described above, and curing the coating film after irradiation to separate the magnetic recording section 10 and the protective plate 7. Glue. Therefore, the UV transmittance of the protective plate 7 is 80%.
The following is preferable.

Examples of these materials include transparent inorganic materials such as glass, and various transparent or semitransparent resin materials such as polycarbonate, AS resin, ABS resin, acrylic resin, polyethylene, polyvinyl chloride, polystyrene, and polypropylene. , various thermoplastic resins (especially transparent grades) such as polymethylpentene, and various thermosetting resins (especially transparent grades) such as epoxy resins and alkyd resins.

In this case, the protective plate 7 is preferably made of the same resin material as the base 2, which will be described later.

Such a protection plate 7 has almost the same shape as the base 2 described later, and is usually disk-shaped, and has a J2 length of 1.0 to 1.
．． It is about 5 mm.

The magnetic recording section 10, which is bonded to the protective plate 7 via the adhesive layer 6, has the following structure.

That is, as shown in FIG. 1, the base 2 is usually made of resin, such as olefin resin such as acrylic resin, polycarbonate resin, epoxy resin, and polymethylpentene, but may also be made of glass or the like. Good too.

Note that since it is preferable to record through the substrate 2, the transmittance for reading light or reading light is 86%.
The above is necessary.

In addition, the base is usually disk-shaped and has a length of 1.2 to 1.5 m.
It is assumed to be about 12 m.

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

The depth of the groove is about λ/8n, especially λ/7n~
λ/12 n (where n is the refractive index of the substrate)
It is said that Further, the groove Ill is approximately equal to the track rj1.

It is preferable that the magnetic thin film layer located at the four parts of the groove be used as a recording track part, and write light and read light are irradiated from the back side of the substrate.

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

Note that other shapes of the base may be a tape, a drum, or the like.

On such a substrate 2, a magnetic thin film layer 4 is formed directly or, more preferably, via an intermediate layer 3.

Information is magnetically recorded in this magnetic thin film layer 4 by a modulated heat beam or a modulated magnetic field, and the recorded information is reproduced by magneto-optical conversion.

As such a magnetic thin film layer 4, an alloy of a rare earth metal and a transition metal is formed as an amorphous film with a normal thickness by sputtering, vapor deposition, or the like.

There are various rare earth metals and transition metals, but particularly preferred are Gd and Tb as the 11η metals, and Fe and Co as the latter.

A suitable example thereof is GdFe.

TbFe, TbFeCo, GdFeCo.

There are GdTbFe and the like.

In these cases, the amount of rare earth metals is about 15 to 35 aL%, and the amount of transition metals is about 65 to 85 at%.

Also magnetic? ! ! The thickness of the membrane layer 4 is approximately 0.05 to 0.1 μI.

In addition, when forming the magnetic thin film layer 4 through the intermediate layer 3 as shown in the figure, the material of the intermediate layer 3 is 5i02,
Sin, A.I.N.

Examples include those formed of Si3N4, ZnS, etc. by vacuum evaporation, sputtering, or the like.

Such an intermediate layer 3 has a thickness of 0.05 to 0.2 μI.

As shown in the figure, it is preferable to provide an inorganic protective layer 5 of silicon oxide, silicon nitride, Al12o3, A42N, etc. on the magnetic thin film layer 4 of the present invention.

When this protective layer 5 is provided, a protective plate 7 is adhered onto this protective layer 5 via the adhesive layer 6 described above, and the medium 1 is constructed.

The thickness of the protective layer 5 is usually about 0.05 to 0.2 .mu.I, and the layer formation method may be the same as that for the intermediate layer 3 described above.

Further, the surface of the substrate 2 (the side of the magnetic thin film layer) may be subjected to plasma treatment, or a plasma polymerized film may be provided on the surface of the substrate 2. These may be used in combination.

In these cases, the adhesive strength between the base 2 and the magnetic thin film layer 4 is improved.

Furthermore, it is preferable to provide a hard coat layer as various protective layers on the back surface of the substrate 2 and the protective plate 7 (the surface on which the IF-sensitive thin film layer is not provided).

The material of the hard coat layer may be the same as that of the adhesive layer 6 described above.

■Specific effects of the invention In the magneto-optical recording medium of the present invention, the magnetic thin film layer F of the magnetic recording section having a magnetic thin film layer on the base is protected by an adhesive layer containing an ultraviolet-cured compound. It is made up of boards that are glued together.

Therefore, this product has excellent durability and storage stability in a high humidity atmosphere, and the productivity of the medium is also extremely high.

(2) Specific Examples of the Invention The present invention will be explained in further detail by showing specific examples of the present invention.

I[';t
The layer thickness was 0.09 μm.

Furthermore, a magnetic thin film layer 4 shown below was provided on top of this.

(Formation of magnetic thin film layer) A thin alloy film made of TbFeCo was deposited to a thickness of 0.1 μI by sputtering to form a magnetic thin film layer.

Note that the target used was an Fe target with Tb and Co chips placed on it.

Furthermore, a 5i02 protective layer 5 was formed on the magnetic thin film layer 4 to a thickness of 0.9 μm by sputtering, and the protective layer 5 contained the following ultraviolet curable compound.
The coating composition was applied with a spinner coat.

(Coating composition) Coating composition (invention) Multifunctional oligoester acrylate (UV-3495HV, manufactured by Toagosei Co., Ltd.)
(Invention) Multifunctional oligoester acrylate (LA-3620, manufactured by Toyo Ink Co., Ltd.) Miseiai Goayu (comparison) EVA (ethylene vinyl acetate copolymer) is coated as a protective layer, and a synthetic rubber-based Hot melt adhesive (H
M-1275 (manufactured by Nippon Fuller Co., Ltd.) was applied, and then a polycarbonate protection plate 7 with a diameter of 13 cm was brought into close contact with the surface of this coating film.

For coating A1 compositions 1 and 2, the J7 thickness of the coating film is 20μ
m, and then irradiated with ultraviolet rays of 120 W/cm for 15 seconds from above the protective plate to cure crosslinking.

In the case of Coating Composition 3, the hot melt adhesive was applied to a thickness of 20 μm without using the above method, and then allowed to harden naturally.

In this way, various samples as shown in Table 1 below were prepared and the above properties were evaluated.

(1) C/N ratio (deterioration on storage) The initial C/N ratio and the amount of change in the C/N ratio after storage at 60° C. and 90% RH for 1000 hours were measured under the following conditions.

Rotation speed 4 m/sec Carrier frequency IMIlz resolution
30KIlz recording power (830r+m)
3~4mW reproduction power (830nm) l m
14(2) Pit error rate The pit error rate of the EFM signal was measured at the initial stage and after storage for 1000 hours at 60° C. and 90% RH.

The results are shown in Table 1.

Table 1 From the results in Table 1, the effects of the present invention are clear.

BRIEF DESCRIPTION OF THE 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, 3... Intermediate layer, 4... Magnetic thin film layer, 5... Protective layer, 6... Ultraviolet curing adhesive layer , 7...Protective plate, lO...Magnetic recording department, Applicant: TDC Co., Ltd. Agent, Patent attorney: Yo Ishii -1%:. (~

Claims (2)

[Claims] (1) A radiation-curing type having a magnetic recording section having an amorphous perpendicular magnetic thin film layer of rare earth-transition metal on a substrate, and a radiation-curing type that is cured by ultraviolet rays on the surface of the amorphous perpendicular magnetic thin film layer side of the magnetic recording section. A magneto-optical recording medium characterized in that a protective plate is adhered via an adhesive layer containing a compound. (2) The magneto-optical recording medium according to claim 1, wherein the protective plate and the base are made of the same resin material.