JP2735575B2 - Magneto-optical recording medium - Google Patents

Description

The present invention relates to a magneto-optical recording medium in which an enhancement layer, a magneto-optical recording layer, and a protective layer are sequentially laminated on a signal surface of a substrate. It relates to the composition of the enhancement layer and the protective layer.

[Conventional technology]

2. Description of the Related Art A magneto-optical recording medium in which an enhancement layer, a magneto-optical recording layer, and a protective layer are sequentially laminated on a signal surface of a substrate has been known.

The enhance layer repeatedly reflects the reflected light from the magneto-optical recording layer, and increases the apparent Kerr rotation angle to increase the CN.
For example, silicon nitride (SiN), aluminum nitride (AlN), zinc sulfide (Zn
S), silicon oxide (SiO), aluminum oxide (Al
₂ O ₃ ), formed of a dielectric such as silicon carbide (SiC). The enhanced layer also has a function of preventing moisture permeation from the substrate side. On the other hand, the protective layer is provided to harden the surface of the magneto-optical recording layer to prevent damage to the magneto-optical recording layer due to collision of foreign matter and to prevent moisture permeation to the magneto-optical recording layer.

As described above, since the enhancement layer and the protective layer have the same function in terms of preventing moisture permeation, the purpose is to reduce the size of the film forming apparatus, reduce the number of types of targets, and reduce the number of steps required for replacing targets. Conventionally, the protective layer is formed of the same material as the enhance layer.

By the way, among the above-mentioned materials for the enhancement layer and the material for the protective layer, the oxide-based compound is more likely to use a non-oxide-based compound because oxygen contained therein may deteriorate the magneto-optical recording layer. It is preferred.
Also, when a non-oxide thin film is formed by sputtering, if pure argon gas is used as the introduction gas and the gas pressure in the vacuum chamber is set high, the refractive index of the formed thin film becomes too large, and As a result, the recording / reproducing characteristics deteriorate.

For this reason, conventionally, when sputtering a non-oxide-based enhanced layer, for example, a nitride enhanced layer, an argon gas to which about 10% of nitrogen gas is added as a sputter gas is used, and the gas pressure in the vacuum chamber is reduced. The method used when setting it relatively low is adopted. It is not necessary to adjust the refractive index of the protective layer functionally, but it is formed in the same manner as the enhance layer from the viewpoint of improving the productivity described above.

[Problems to be solved by the invention]

However, a magneto-optical recording medium having an enhancer layer and a protective layer having exactly the same composition and formed by the above-described method may cause cracks in the enhancer layer and the protective layer within a short time when left in a high-temperature and high-humidity environment. It was found that there was a problem in practicality in terms of environmental resistance.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to improve the durability of a magneto-optical recording medium in a high-temperature and high-humidity environment.

[Means for solving the problem]

The present invention, in order to achieve the above object, on the signal surface of the substrate, an enhanced layer formed of a dielectric containing a non-oxide compound and a smaller amount of an oxide compound than this,
In a magneto-optical recording medium in which a magneto-optical recording layer and a protective film formed of the same kind of dielectric material as the enhance layer are sequentially laminated, the content of the oxide contained in the protective layer is set to the enhance layer. The configuration is such that it is higher than the content of the contained oxide.

[Action]

In a dielectric thin film containing a non-oxide compound and a smaller amount of an oxide compound, a dielectric thin film having a high oxide content is compared with a dielectric thin film having a low oxide content. Therefore, ductility and coefficient of thermal expansion increase. When a protective layer having a large ductility and a large coefficient of thermal expansion is laminated on an enhanced layer having a small ductility and a small coefficient of thermal expansion via a magneto-optical recording layer, the average ductility and the coefficient of thermal expansion of the laminate laminated on the substrate are increased. Therefore, the crack of the enhance layer and the protective layer in a high temperature and high humidity environment can be prevented without deteriorating the optical properties of the enhance layer, and the durability of the magneto-optical recording medium is improved.

In addition, when forming the enhance layer and the protective layer, the inside of the vacuum chamber is evacuated to a predetermined high vacuum degree, and then a sputter gas such as an inert gas is introduced.
It is practically impossible to completely exhaust the air in the vacuum chamber no matter how high the vacuum is drawn, and a small amount of oxygen mixed in the spatter gas cylinder is introduced into the vacuum chamber with the introduction of the spatter gas. In some cases, when a resin substrate is used, air may be released from the substrate.

As described above, it is considered that a small amount of oxygen is present in the vacuum chamber, but the higher the gas pressure in the vacuum layer and the higher the content of the mixed gas mixed in the inert gas, the higher the spatter particles and The proportion of oxygen incorporated in the formed thin film increases. Therefore, by appropriately adjusting the sputter conditions for forming the enhanced layer and the sputter conditions for forming the protective layer, the protective layer having a high oxide content and the enhanced layer having a low oxide content are appropriately adjusted. And can be formed.

〔Example〕

As shown in FIG. 1, a magneto-optical recording medium according to the present invention comprises an enhancement layer 3 on a surface of a substrate 1 on which a signal pattern 2 is formed.
And the magneto-optical recording layer 4 and the protective layer 5 are sequentially laminated.

The substrate 1 is made of, for example, transparent ceramics such as glass,
It is formed of a transparent resin material such as polycarbonate (PC), polymethyl methacrylate (PMMA), polymethyl pentene, and epoxy. On one surface of the substrate 1, signal turns 2 such as guide grooves corresponding to tracking signals and prepits corresponding to address signals are formed. The planar shape of the substrate 1 can be formed in an arbitrary shape as required, such as a disk shape or a card shape.

As a means for forming the signal pattern 2, an appropriate method is applied depending on the material of the substrate 1.

For example, when the substrate 1 is formed of a thermoplastic resin such as PC, PMMA, and polymethylpentene, the molten substrate material is injected into an injection molding die to connect the substrate 1 and the signal pattern 2 to each other. The so-called integral extrusion method of integrally molding is suitable. As for the substrate material, a forming method such as a so-called compression method or an injection-compression method for applying pressure after injecting a molten substrate material into an injection molding die may be applied. it can. Further, when the substrate 1 is formed of ceramics such as glass or a thermosetting resin such as epoxy, light is emitted between the substrate 1 and a stamper (die) on which a desired signal turn inversion pattern is formed. Expand the curable resin,
The so-called 2P method (photo-polymerization; photocurable resin method) of transferring the inverted pattern of the stamper to the substrate 1 is suitable.
As for a thermosetting resin such as epoxy, a so-called casting method in which a substrate material in a molten state is injected into a mold by intravenous injection and the substrate 1 and the signal pattern 2 are integrally formed can be applied.

The enhancement layer 3 is made of a nitride of a metal element, a carbide of a metal element, a fluoride of a metal element, a sulfide of a metal element, a hydride of a metal element, a nitride of a nonmetal element, a carbide of a nonmetal element, a nonmetallic carbide. It is formed of a material having a low oxide dielectric content, such as a fluoride of an element, a sulfide of a nonmetallic element, or a hydride of a nonmetallic element. As the metal element forming the compound, any metal element can be used, and in particular, aluminum, cobalt, chromium,
Iron, germanium, hafnium, indium, magnesium, molybdenum, niobium, tin, tantalum, titanium,
Those selected from tungsten, zinc and zirconium are preferred. In addition, as the nonmetallic element forming the compound, one selected from boron and silicon is particularly preferable.

The enhancement layer 3 adjusts the refractive index to a desired value, that is, an X-ray photoelectron in order to adjust the refractive index to a value required to exhibit an enhancement effect and not to decrease the amount of recording / reproducing light applied to the recording film 4. The oxide content by spectroscopic analysis is adjusted to 10% to 20%.

The recording layer 4 can be formed of any known magneto-optical recording material such as an amorphous alloy containing terbium, iron, and cobalt.

The protective layer 5 is formed with a compound of the same kind as the compound forming the enhance layer 3. However, in order to make the ductility and the coefficient of thermal expansion larger than those of the enhance layer 3, the content of the oxide by X-ray photoelectron spectroscopy is determined. Has been adjusted to 15% to 40%.

In the magneto-optical recording medium of the above embodiment, the enhancement layer 3 is formed of a substance having a low oxide content, and the refractive index thereof is adjusted to a desired value, so that the enhancement effect is high. Further, the protective layer 5 is formed of a substance having a high oxide content,
Since the ductility and the coefficient of thermal expansion are made larger than that of the enhance layer 3, the average ductility and the coefficient of thermal expansion of the laminated body laminated on the substrate become larger than that of the enhance layer itself. Cracking of the protective layer can be prevented.

Further, since a material having a low oxide content is used as the material for the enhance layer and the material for the protective layer, the recording layer 4 is hardly attacked by oxygen contained in the enhance layer 3 and the protective layer 5, In addition, the protective effect of the recording layer is high because of its high moisture-proof property.

Next, the method for manufacturing a magneto-optical recording medium according to the present invention will be described in the second.
The description will be made according to the flowchart in the figure.

First, in step S-1, the substrate on which the signal pattern is formed is housed in the vacuum chamber of the sputtering apparatus.
The vacuum chamber is evacuated to a predetermined degree of vacuum. The degree of vacuum at this time is determined in consideration of the purity required for the thin film and the operation time.

Next, in step S-2, the type and gas pressure of the gas introduced into the vacuum chamber are adjusted so that an enhanced layer having a low oxide content and a desired refractive index is formed on the substrate, In step S-3, the enhancement layer is sputtered.

Next, in step S-4, the kind and pressure of the gas introduced into the vacuum chamber are adjusted so that a desired recording layer is formed on the enhanced layer, and in step S-5, sputtering of the recording layer is performed. Do.

Further, in step S-6, the type and pressure of the gas introduced into the vacuum chamber are adjusted so that a protective layer having a high oxide content and a high ductility and a high coefficient of thermal expansion is formed on the recording layer. Then, in step S-7, sputtering of the protective layer is performed.

In the method of manufacturing the magneto-optical recording medium of the embodiment, each time the layers are sputtered, the type and the gas pressure of the gas introduced into the vacuum chamber are adjusted, so that the enhanced layer having desired physical properties and A protective layer can be easily formed.

Hereinafter, more specific examples and comparative examples according to the related art will be described, and effects of the present invention will be referred to.

First Example A vacuum chamber containing a resin substrate was evacuated to 3 × 10 ⁻⁵ (Pa).

Then, an argon gas mixed with 10% nitrogen gas is introduced into the vacuum chamber to equilibrate the gas pressure in the vacuum chamber to 0.2 (Pa), and a silicon nitride-based enhanced layer is formed on the signal surface of the substrate by 850 mm. Sputtered to a thickness of ~ 900 mm.

Next, once the gas in the vacuum chamber is evacuated, pure argon gas is introduced to balance the gas pressure in the vacuum chamber to 0.2 (Pa), and a terbium-iron-cobalt-based recording layer is formed on the enhanced layer. Sputtered to a thickness of about 1000 mm.

Further, after the gas in the vacuum chamber is evacuated again, pure argon gas is introduced to equilibrate the gas pressure in the vacuum chamber to 1.0 (Pa), and a silicon nitride-based protective layer is formed on the recording layer by about 10 μm.
Sputtered to a thickness of 00 mm.

<Second embodiment> After the enhancement layer and the recording layer are sequentially laminated on the signal surface of the resin substrate by the same method as the first embodiment, the gas in the vacuum chamber is exhausted, and pure nitrogen gas is introduced into the vacuum chamber. The gas pressure in the vacuum chamber was equilibrated to 0.2 (Pa), and a silicon nitride-based protective layer was sputtered on the recording layer to a thickness of about 1000 mm.

<Third Embodiment> After the enhancement layer and the recording layer are sequentially laminated on the signal surface of the resin substrate by the same method as the first embodiment, the gas in the vacuum chamber is exhausted, and the argon gas and the nitrogen gas are injected in the vacuum chamber. And 50
The gas pressure in the vacuum chamber was reduced to 0.
After equilibrating to 5 (Pa), a silicon nitride-based protective layer was sputtered on the recording layer to a thickness of about 1000 mm.

<Comparative Example> When forming the enhancement layer and the protective layer, argon gas mixed with 10% nitrogen gas was introduced into the vacuum chamber, and the gas pressure in the vacuum chamber was equilibrated to 0.2 (Pa) to perform sputtering. Went.

Other conditions except for the type of gas to be introduced and the gas pressure in the vacuum chamber are the same as those in the first to third embodiments.

The magneto-optical recording medium of each of the above Examples and Comparative Examples was heated to a temperature of 60.
When left in an environment of 90 ° C. and a relative humidity of 90%, the magneto-optical recording medium of the comparative example cracked in a part of the enhancement layer and the protective layer after 20 hours, and after 100 hours, the cracks occurred in the enhance layer and the protective layer. While the cracks spread throughout the magneto-optical recording medium according to the present invention, no cracks were observed even after lapse of 2,000 hours.

In the above embodiment, only silicon nitride was described as an example, but other metal or nonmetal sulfides,
Similar effects are obtained for carbides, hydrides and the like.

〔The invention's effect〕

As described above, the present invention relates to a magneto-optical recording medium in which an enhancement layer, a magneto-optical recording layer, and a protective layer are laminated in this order on the signal surface of a substrate, and the content of the oxide contained in the protective layer is reduced to the enhanced layer. Since the content is higher than the content of the contained oxide, the average ductility and the coefficient of thermal expansion of the laminated body laminated on the substrate are increased, and the durability of the magneto-optical recording medium in a high-temperature and high-humidity environment is improved. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a magneto-optical recording medium according to the present invention, and FIG. 2 is a flowchart for explaining the manufacture of the magneto-optical recording medium according to the present invention. 1: substrate, 2: signal pattern, 3: enhanced layer, 4: recording layer,
5: protective layer.

Claims (4)

(57) [Claims] 1. An enhancement layer formed on a signal surface of a substrate by a dielectric containing a non-oxide compound and a smaller amount of an oxide compound than the compound, a magneto-optical recording layer, and the enhancement layer. In a magneto-optical recording medium in which a layer and a protective film formed of the same kind of dielectric are sequentially laminated, the content of the oxide contained in the protective layer is determined by the content of the oxide contained in the enhanced layer. A magneto-optical recording medium characterized by having a higher height. 2. The magneto-optical recording medium according to claim 1, wherein the enhance layer and the protective layer are formed of a dielectric containing silicon nitride and a smaller amount of silicon oxide. Magnetic recording medium. 3. The magneto-optical recording medium according to claim 1, wherein said substrate is formed of a resin material. 4. The magneto-optical recording medium according to claim 1, wherein said protective layer is formed of a thin film having higher ductility and a higher coefficient of thermal expansion than said enhanced layer.