JPH0258746A - Magneto-optical recording medium and production thereof - Google Patents

Abstract

PURPOSE:To improve durability in high-temp. and high humidity environment by increasing the content of the oxide contained in a protective layer to the ratio higher than the content of the oxide contained in an enhancement layer. CONSTITUTION:The content of the oxide contained in the protective layer 5 formed of a material essentially consisting of a compd. of a nonoxide system is increased to the ratio higher than the content of the oxide contained in the enhancement layer 3 formed of the material likewise essentially consisting of the compd. of the nonoxide system. Namely, the thin film essentially consisting of the nonoxide system contg. the oxide at the high ratio is higher in the ductility and coefft. of thermal expansion than the thin film essentially consisting of the compd. of the nonoxide system contg, the oxide at a low ratio. The average ductility and coefft. of thermal expansion of the laminated body laminated on a substrate 1 increase. The cracking of the enhancement layer 3 and the protective layer 5 under the high-temp. and high-humidity envi ronment is prevented in this way without deteriorating the optical properties of the enhancement layer 3. The durability of the magneto-optical recording medium is thus improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magneto-optical recording medium and a method for manufacturing the same;
In particular, the present invention relates to compositions of enhancement layers and protection layers, and methods for efficiently forming enhancement layers and protection layers with desired compositions.

[Conventional technology]

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

The enhancement layer repeatedly reflects the reflected light from the magneto-optical recording layer, increases the apparent Kerr rotation angle, and improves the CN.
For example, silicon nitride (
SiN), aluminum nitride (AIN), zinc sulfide (Z
nS), silicon oxide (Sin), aluminum oxide (
A 1.20:l), and is formed of a dielectric material such as silicon carbide (SiC). In addition, this enhanced layer includes
It also has the 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 collisions with foreign objects, and to prevent moisture from permeating into the magneto-optical recording layer.

In this way, the enhancement layer and the protective layer have the same function in terms of preventing moisture permeation, so it is possible to reduce the size of the film forming equipment, reduce the number of types of Targetera 1-, and save the man-hours required for replacing targets. To achieve this goal, the protective layer has conventionally been formed of the same material as the enhancement layer.

By the way, among the above-mentioned enhancement layer materials and protective layer materials, it is preferable to use non-oxide compounds because the oxygen contained in oxide compounds may deteriorate the magneto-optical recording layer. It is considered preferable. In addition, when forming a non-oxide thin film by sputtering, if pure argon gas is used as the introduced gas and the gas pressure in the vacuum chamber is set high, the refractive index of the formed thin film will become too large. Recording/playback characteristics deteriorate.

For this reason, conventionally when sputtering a non-oxide based enhancement layer, such as a nitride enhancement layer, argon gas to which about 10% nitrogen gas is added is used as the sputtering gas, and the gas pressure in the vacuum chamber is A method is used to set the value relatively low. Although it is not necessary to adjust the refractive index of the protective layer functionally, it is formed in the same manner as the enhancement layer from the viewpoint of improving productivity as described above.

[Problem that the invention seeks to solve]

However, a magneto-optical recording medium having an enhancement layer and a protective layer having exactly the same composition formed by the method described above is
It was found that when left in a high-temperature environment, the enhancement layer and protective layer cracked within a short period of time, causing problems in practicality in terms of environmental resistance.

The present invention aims to solve the above-mentioned drawbacks of the prior art and improve durability under high temperature and high humidity environments.

[Means to solve the problem]

In order to achieve the above object, the present invention reduces the content of oxides contained in a protective layer formed of a substance mainly composed of non-oxide compounds. It is characterized in that the content of oxides is higher than the content of oxides contained in the enhancement layer formed of the constituent substances.

In addition, the sputtering conditions for forming the enhancement layer and the sputtering conditions for forming the protective layer are changed for at least one of the type of gas introduced into the vacuum chamber and the gas pressure within the vacuum chamber. The manufacturing feature is that the

[Effect]

A thin film whose main component is a non-oxide compound with a high oxide content has higher ductility and coefficient of thermal expansion than a thin film whose main component is a non-oxide compound with a low oxide content. Become. When a protective layer with high ductility and coefficient of thermal expansion is laminated on an enhancement layer with low ductility and coefficient of thermal expansion via a magneto-optical recording layer, the average ductility and coefficient of thermal expansion of the laminate stacked on the substrate will increase by 2. do. Therefore, it is possible to prevent the enhancement layer and the protective layer from cracking in a high temperature and high humidity environment without deteriorating the optical properties of the enhancement layer, and the durability of the magneto-optical recording medium is improved.

In addition, when forming the enhancement layer and the protective layer, the inside of the vacuum chamber is evacuated to a predetermined high degree of vacuum, and then a sputtering gas such as an inert gas is introduced. However, it is virtually impossible to completely exhaust the air in the vacuum chamber, and a small amount of oxygen mixed in the sputtering gas cylinder may be introduced into the vacuum chamber when the sputtering gas is introduced. Furthermore, when a resin substrate is used, air may be released from the substrate.

In this way, it is thought that a small amount of oxygen exists 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 more the sputtered particles and The proportion of oxygen taken into the formed thin film increases. Therefore, by appropriately adjusting the sputtering conditions when forming the enhancement layer and the sputtering conditions when forming the protective layer, it is possible to form a protective layer with a high oxide content and an enhancement layer with a low oxide content. can do.

〔Example〕

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

The substrate 1 is made of, for example, transparent ceramics such as glass, polycarbonate (PC), polymethyl methacrylate (
It is formed from a transparent resin material such as PMMA), polymethylpentene, or epoxy.

A signal pattern 2 such as a guide groove corresponding to a tracking signal and a prepit corresponding to an address signal is formed on one side of the substrate 1. Note that the planar shape of the substrate 1 can be formed into any 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 made of PC, PMMA, or a thermoplastic resin such as polymethylpentene, the substrate 1 and the signal pattern 2 are formed by injecting the molten substrate material into an injection mold. A so-called injection method of integrally molding is suitable. Regarding this substrate material, it is also possible to apply a forming method such as the so-called compression method or injection-combination method, in which pressure is applied after injecting the molten substrate material into an injection mold. Further, when the substrate 1 is made of ceramics such as glass or thermosetting resin such as epoxy, light is generated between the substrate 1 and a stamper (mold) on which an inverted pattern of the desired signal pattern is formed. So-called 2P, in which the curable resin is spread and the inverted pattern of the stamper is transferred to the substrate 1.
Law (Photo.

Polymerization (photocurable resin method) is suitable. Furthermore, with regard to thermosetting resin such as epoxy, a so-called casting method may be applied in which the substrate 1 and the signal pattern 2 are integrally molded by intravenously injecting the substrate material in a molten state into a mold.

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 non-metal element, a carbide of a non-metal element, a non-metal element. It is formed of a substance whose main component is a dielectric other than an oxide-based dielectric, such as a fluoride of a metal element, a sulfide of a non-metal element, or a hydride of a non-metal element. Any metal element can be used as the metal element for forming the compound, but aluminum, cobalt, chromium,
Iron, germanium, hafnium, indium, magnesium, molybdenum, niobium, tin, tantalum, titanium,
Preference is given to those selected from tungsten, zinc and zirconium. Furthermore, as the nonmetallic element for forming the compound, one selected from boron and silicon is particularly suitable.

The enhancement layer 3 is provided with X-ray photoelectrons in order to adjust the refractive index to a desired value, that is, a value necessary for producing an enhancement effect and not reducing the amount of recording/reproducing light irradiated onto the recording film 4. The content of oxides determined 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 whose main components are terbium, iron, and cobalt.

The protective layer 5 is formed of the same kind of compound as the compound forming the enhancement layer 3, but in order to make the ductility and coefficient of thermal expansion larger than that of the enhancement layer 3, the oxide content is 15% as determined by X-ray photoelectron spectroscopy. % to 40%.

The magneto-optical recording medium of the above embodiment has a high enhancement effect because the enhancement layer 3 is formed of a material with a low oxide content and its refractive index is adjusted to a desired value. In addition, since the protective layer 5 is formed of a material with a high oxide content and its ductility and coefficient of thermal expansion are made larger than those of the enhancement layer 3, the average ductility and thermal expansion of the laminate stacked on the substrate are This makes it possible to prevent the enhancement layer and the protective layer from cracking in high-temperature environments.

In addition, since substances containing compounds other than oxides as the main component were used as the enhancement layer material and the protection layer material, it is unlikely that the recording layer 4 would be attacked by the oxygen contained in the enhancement layer 3 and the protection layer 5. Moreover, since it has high moisture resistance, it has a high protective effect on the recording layer.

Next, a method for manufacturing a magneto-optical recording medium according to the present invention will be explained according to the flowchart shown in FIG.

First, in step S-1, a substrate on which a signal pattern has been formed is placed in a vacuum chamber of a sputtering apparatus, and 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 working time.

Next, in step S-2, the type and gas pressure of the gas introduced into the vacuum chamber are adjusted so that an enhancement layer with a low oxide content and a desired refractive index is formed on the substrate, In step S3, an enhancement layer is sputtered.

Next, in step S-4, the type and gas pressure of the gas introduced into the vacuum chamber are adjusted so that a desired recording layer is formed on the enhancement layer, and in step S-5, the recording layer is sputtered. conduct.

Furthermore, in step S-6, the type and gas pressure of the gas introduced into the vacuum chamber are adjusted so that a protective layer with a high oxide content, high ductility, and high coefficient of thermal expansion is formed on the recording layer. Then, in step S7, a protective layer is sputtered.

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

Hereinafter, the effects of the present invention will be described with reference to more specific examples and comparative examples related to the prior art.

<First example> A vacuum chamber containing a resin substrate was heated to 3X10-5 (Pa).
I vacuumed it up.

Next, argon gas mixed with 10% nitrogen gas was introduced into the vacuum chamber to reduce the gas pressure in the vacuum chamber to 0.2 (Pa
), and a silicon nitride-based enhancement layer was sputtered on the signal surface of the substrate to a thickness of 850× to 900×.

Next, after exhausting the gas in the vacuum chamber, pure argon gas is introduced to reduce the gas pressure in the vacuum chamber to 0.2 (Pa).
A terbium-iron-copal 1-based recording layer was sputtered on the enhancement layer to a thickness of about 1000×.

Furthermore, after exhausting the gas in the vacuum chamber again, pure argon gas is introduced to increase the gas pressure in the vacuum chamber to 1. 0 (Pa)
A silicon nitride-based protective layer was sputtered on the recording layer to a thickness of about 1000 nm.

<Second Example> After sequentially laminating an enhancement layer and a recording layer on the signal surface of a resin substrate using the same method as in the first example, the gas in the vacuum chamber was evacuated, and pure nitrogen gas was introduced into the vacuum chamber. The gas pressure in the vacuum chamber was then equilibrated to 0.2 (Pa), and a silicon nitride-based protective layer was sputtered on the recording layer to a thickness of about 1000 nm.

<Third Example> After sequentially laminating an enhancement layer and a recording layer on the signal surface of a resin substrate using the same method as in the first example, the gas in the vacuum chamber was evacuated, and argon gas and nitrogen gas were added to the vacuum chamber. Toga 50
The gas pressure in the vacuum chamber is reduced to 0 by introducing the mixed gas in % increments.
．． 5 (Pa), and a silicon nitride-based protective layer was sputtered on the recording layer to a thickness of about 1000 nm.

<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). sputtering was performed.

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

The magneto-optical recording media of each of the above Examples and Comparative Examples were heated to 60°C.
When left in an environment with a relative humidity of 90% at °C, the magneto-optical recording medium of the comparative example developed cracks in part of the enhancement layer and the protective layer after 20 hours, and after 100 hours, the enhancement layer and the protective layer did not crack. While the cracks spread throughout the entire area, the magneto-optical recording medium according to the present invention had 2 cracks.
No cracks were observed even after 1,000 hours had passed.

In the above embodiments, only silicon nitride was used as an example, but similar effects can be obtained with other metals or nonmetals such as sulfides, carbides, and hydrides.

〔Effect of the invention〕

As explained above, since the magneto-optical recording medium of the present invention has the content of oxides contained in the enhancement layer and the protective layer appropriately adjusted, it can withstand high temperature and high humidity environments without deteriorating the optical properties of the enhancement layer. The durability of the underlying magneto-optical recording medium can be improved.

Furthermore, the method for manufacturing a magneto-optical recording medium of the present invention includes changing the type of gas introduced into the vacuum chamber and the gas pressure within the vacuum chamber as appropriate when forming the enhancement layer and the protective layer. Therefore, an enhancement layer having a low oxide content and a desired refractive index and a protective layer having a high oxide content and high ductility and coefficient of thermal expansion can be formed.

[Brief explanation of the drawing]

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 illustrating the manufacturing of the magneto-optical recording medium according to the present invention. +-: Board, 2: Signal pattern, 3: Enhancement chart basic information/Duinenhanha two-layer drunkenness imperial marriage tank Jugo 1

Claims (8)

[Claims] (1) On the signal surface of the substrate, an enhancement layer formed of a dielectric material mainly composed of a non-oxide compound, a magneto-optical recording layer, and a protective layer formed of the same type of compound as the enhancement layer. What is claimed is: 1. A magneto-optical recording medium comprising sequentially laminated layers, characterized in that the content of oxides contained in the protective layer is higher than the content of oxides contained in the enhancement layer. (2) The magneto-optical recording medium according to claim 1, wherein the enhancement layer and the protective layer are formed of a compound containing silicon nitride as a main component. (3) A magneto-optical recording medium according to claim 1, wherein the substrate is made of a resin material. (4) The magneto-optical recording medium according to claim 1, wherein the protective layer is formed of a thin film having higher ductility and coefficient of thermal expansion than the enhancement layer. (5) In a method for manufacturing a magneto-optical recording medium in which an enhancement layer, a magneto-optical recording layer and a protective layer are sequentially deposited on the signal surface of a substrate by sputtering, the sputtering conditions for forming the enhancement layer and the protective layer are 1. A method for manufacturing a magneto-optical recording medium, characterized in that sputtering conditions during formation are changed with respect to at least one of the type of gas introduced into the vacuum chamber and the gas pressure within the vacuum chamber. (6) In the method for manufacturing a magneto-optical recording medium according to claim 5, when forming the enhancement layer, nitrogen gas is
0% mixed argon gas is introduced to adjust the gas pressure in the vacuum chamber to 0.2 (Pa), and when forming the protective layer, pure argon gas is introduced to adjust the gas pressure in the vacuum chamber to 0.2 (Pa). Pressure 1
．． 1. A method for manufacturing a magneto-optical recording medium, characterized in that the pressure is adjusted to 0 (Pa). (7) In the method for manufacturing a magneto-optical recording medium according to claim 5, when forming the enhancement layer, nitrogen gas is
0% mixed argon gas is introduced to adjust the gas pressure in the vacuum chamber to 0.2 (Pa), and when forming the protective layer, pure nitrogen gas is introduced to adjust the gas pressure in the vacuum chamber to 0.2 (Pa). pressure 0.2
(Pa). (8) In the method for manufacturing a magneto-optical recording medium according to claim 5, when forming the enhancement layer, nitrogen gas is
When forming the protective layer by introducing 0% mixed argon gas and adjusting the gas pressure in the vacuum chamber to 0.2 (Pa), argon gas and nitrogen gas are mixed at 50% each. 1. A method for manufacturing a magneto-optical recording medium, characterized in that the gas pressure in the vacuum chamber is adjusted to 0.5 (Pa) by introducing a gas.