JPH01201845A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To prevent oxidation of magneto-optical recording layers and to obtain a long-life recording medium by allowing a gaseous phase rust inhibitor to exist in the air sandwich space of the recording medium of an air sandwich type having the above-mentioned recording layers. CONSTITUTION:A magneto-optical disk veneer is formed by laminating an inorg. glass layer 2, an enhancement layer 3, a magnetic recording layer 4 and an inorg. glass layer 2 on a substrate 1. Two sheets of the veneers are then disposed in such a manner that the layers 4 are positioned on the inside and spacers 6, 7 and rust inhibitive paper 5 are held in place between these substrates, then the substrates are stuck to each other by a UV curing adhesive agent 8. A part 9 which is not coated with the adhesive agent 8 is provided as the vent hole of the air space to a part of the inside circumferential spacer 6. The gaseous phase rust inhibitor formed by impregnating cyclohexylamine nitrite into linter paper is used as the rust inhibitive paper 5 and is made to exist in the air space. The oxidation of the recording layers by the oxygen and moisture in the air is thereby prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magneto-optical recording medium. More specifically, the present invention relates to improving the corrosion resistance of air sandwich type magneto-optical recording media.

(Prior Art) Conventionally, there is a magneto-optical disk which is used for erasable and rewritable high-density memory and is recorded by heating by light irradiation and can be read using magneto-optical effects such as the magnetic Kerr effect and the Faraday effect.

Amorphous thin films made of GdTbFeCo are particularly excellent as recording films for magneto-optical disks, and have excellent film forming properties when producing large-area thin films at temperatures near room temperature, and write efficiency for writing signals and small photothermal energy. , readout efficiency for reading written signals with good S/N ratio, large Kerr rotation angle, and Curie point around 1506C,
Optimal as a magneto-optical recording medium.

However, magneto-optical recording layers such as GdTbFeCo generally have a drawback of poor corrosion resistance.

That is, when it comes into contact with air or water vapor, it is oxidized and its magnetic properties deteriorate, and eventually it becomes completely oxidized and becomes transparent.

SiO, 5i02 to prevent oxidation of the recording film.

A recording film is sandwiched between a protective layer of an inorganic material such as Si3N4 or Al2O3, or a halogenated organic resin or ultraviolet curable acrylic resin has moisture-proofing properties.

A method of coating a recording film with a thermosetting epoxy resin has been proposed.

(Problem to be Solved by the Invention) However, when the recording layer is covered with a protective layer, the apparent recording sensitivity decreases because the optical energy is also absorbed by the protective layer when writing and recording is performed by irradiating the laser beam. decreases,
Not only does it require more optical energy, but high-speed writing becomes impossible.

In order to avoid the above drawbacks, an air sandwich type magneto-optical disk has been proposed. This disk is designed to prevent the recording layer from being oxidized by filling the air space with inert gas, but because of this, it has a sealed structure, and due to pressure fluctuations in the outside air, the inside of the air space may This creates a pressure difference that causes the disc to warp (curve).

Air sandwich type discs usually have ventilation holes to avoid the pressure differences mentioned above.

However, in this case, oxygen and moisture from the outside air flow in and oxidize the recording layer, making it impossible to prevent the recording layer from oxidizing.

(Means for Solving the Problems) The magneto-optical recording medium of the present invention is an air sandwich type magneto-optical recording medium in which at least a magnetic recording layer is laminated on a substrate. The agent is present. The present invention is characterized in that oxidation of the recording layer is suppressed by the presence of nitrites as a specific gas-phase rust preventive agent.

(Preferred embodiment for carrying out the invention) In the air sandwich type magneto-optical recording medium of the present invention, nitrites are present as a vapor phase rust preventive agent in the air space. Specifically, the presence of paper impregnated with cyclohexylamine nitrite or the like is intended to prevent the magnetic recording layer from being oxidized by oxygen or moisture in the air.

The air sandwich type magneto-optical recording medium in which at least a magnetic recording layer is laminated on a substrate referred to in the present invention is not only one in which a direct magnetic recording layer is laminated on a substrate;
It also includes a structure in which a layer such as a protective layer, which will be described in detail later, is laminated on a substrate, and a magnetic recording layer is further laminated thereon.

The air sandwich type is one in which two disks are bonded together with the magnetic recording layer inside and inner and outer spacers sandwiched between them. In this case, only one of the two discs may have a recording layer. Also, regardless of the presence or absence of spacers, unless the entire surface is pasted together,
Any type of bonded disk having an air space within it is included in the air sandwich type of the present invention.

Although cyclohexylamine nitrite exhibits the most remarkable effect as a gas-phase rust preventive agent of the present invention, nitrites of higher aliphatic amines and nitrites of other amine compounds also exhibit similar effects.

Further, although paper is impregnated with a vapor-based rust preventive agent, the same effect can be obtained by impregnating a nonwoven fabric or coating a film in an air space.

If paper or the like impregnated with this vapor-based rust preventive agent is placed in the air space of a magneto-optical recording medium, the magnetic recording layer will be at an angle of 60°.
Oxidation of the recording layer is extremely suppressed even when subjected to high temperature and high humidity conditions such as C290% relative humidity.

The amount of cyclohexylamine nitrite, which is a gas-phase rust preventive agent, impregnated into paper, etc. is 0.1 of cyclohexylamine nitrite.
Paper or non-woven fabric may be impregnated with an aqueous solution with a concentration ranging from 10% to 10%; at a concentration lower than this, the rust prevention effect of the magnetic recording layer cannot be obtained, and at a concentration higher than this, recording will be adversely affected. The layer is easily oxidized. Paper or the like impregnated with a vapor-phase rust preventive agent only needs to be air-dried at room temperature to remove moisture, and a sufficient effect can be achieved if the paper or the like contains about 5% moisture.

When paper or the like impregnated with this vapor phase rust preventive agent is inserted into the air space of an air sandwich type magneto-optical recording medium, it is best if the paper or nonwoven fabric is almost in contact with the recording layer, but it is preferable that the paper or nonwoven fabric is almost in contact with the recording layer. If it comes into close contact with the recording layer, oxidation will be accelerated. Therefore, it is preferable that the paper used be made of a material such as linter paper or nonwoven fabric that has a large amount of non-contact surface with the recording layer. Therefore, it is not preferable to apply a vapor phase rust preventive agent directly onto the recording layer. Even if the coating thickness is as thin as 100 layers, oxidation of the recording layer will be accelerated.

Next, as for how to judge the rust prevention effect, the magnetic recording layer is left under the conditions of 60°C and 190% relative humidity for 250 hours, and the magnetic recording layer becomes oxidized and becomes transparent, and appears as pinholes. It was determined that those with a large number of pinholes had a low rust prevention effect, and those with a small increase in the number of pinholes had a high rust prevention effect.

(Effects of the Invention) The magneto-optical recording medium of the present invention is an air sandwich type magneto-optical recording medium in which at least a magnetic recording layer is laminated on a substrate. Among these, the presence of paper or nonwoven fabric impregnated with cyclohexylamine nitrite has the effect of suppressing the oxidation of the magnetic recording layer due to oxygen and moisture in the air.

(Examples) The present invention will be described in more detail below by way of examples with reference to the drawings.

Example 1 As shown in Fig. 1, an alkali-free glass layer 2 having anti-reflection and moisture-proofing effects was laminated to a thickness of 50 OA by magnetron sputtering on a donut-shaped substrate 1 made of polycarbonate resin with concentric grooves. On top of this, zinc sulfide is laminated to a thickness of 850 Å as an enhancement layer 3, and on top of that, GdTbF with a thickness of 100 OA is layered as a magnetic recording layer 4.
Two single plates of magneto-optical disks each having eCo laminated by sputtering and an alkali-free glass layer 2 of 500 layers each were used as samples for air sandwich bonding.

Next, a 0.5 m/m thick linter paper was cut into a donut shape, immersed in a 3% aqueous cyclohexylamine nitrite solution, and air-dried for 1 hour indoors to obtain rust-proofing paper 5.

The inner circumferential spacer 6 and outer circumferential spacer 7 for air sandwich bonding are 0. '! Use one with a thickness of m/m,
The two disc veneers were bonded together using an ultraviolet curable adhesive 8 with a spacer 6.7 and antirust paper 5 interposed between them so that the recording layer 4 was on the inside. At the same time, a part of the inner circumferential spacer was provided as an air space vent 9 to which no adhesive was applied.

This sample was heated at 60°C and 290% relative humidity for 5 minutes.
After leaving it for 00 hours, the increase in the number of pinholes due to oxidation was examined. The results are shown in Table 1.

Comparative Example 1 Two single plates of the same magneto-optical disk as used in Example 1 were prepared. A 0.5% cyclohexylamine nitrite aqueous solution was flow coated on the recording layer side of this veneer, and 1
The rust prevention layer 10 of 500 people was laminated by leaving it for a while. This 2
Two disks were bonded together with an ultraviolet curing adhesive 8 with the recording layer inside, with an inner circumferential spacer 6 and an outer circumferential spacer 7 having a thickness of 0.7 m/m in between.

This sample was heated at 60°C and 290% relative humidity.
After leaving it for 50 hours, the increase in the number of pinholes due to oxidation was examined. The results are shown in Table 1.

Comparative Example 2 Two single plates of the same magneto-optical disk as used in Example 1 were prepared. The recording layer side of this veneer was bonded together with an ultraviolet curing adhesive 8 with an inner circumferential spacer 6 and an outer circumferential spacer 7 interposed therebetween, without any anti-corrosion treatment.

This sample was heated at 60°C and 290% relative humidity.
After leaving it for 50 hours, the increase in the number of pinholes due to oxidation was examined. The results are shown in Table 1.

How to check the increase in the number of pinholes...60°C2
After 250 hours of 90% relative humidity, the sample was taken out into the room, the upper and lower two disk veneers were peeled off from the spacer, and the pinholes generated in the recording layer were visually observed under the light of a fluorescent lamp and counted.

Table 1

[Brief explanation of the drawing]

FIG. 1 is a front cross-sectional view of an air sandwich type magneto-optical recording medium in which a cyclohexylamine nitrite anticorrosive paper is inserted in Example 1 of the present invention. FIG. 2 is a front sectional view of an air sandwich dive magneto-optical recording medium coated with a rust preventive agent in Comparative Example 1. FIG. 3 is a front cross-sectional view of an air sandwich type magneto-optical recording medium in Comparative Example 2 which has not been subjected to anti-rust treatment. (Explanation of symbols) Substrate 2: Inorganic glass layer 3: Enhancement layer 4: Recording layer 5: Rust prevention paper 6: Inner spacer 7: Outer spacer 8: Adhesive layer 9: Ventilation hole 10: Rust prevention layer Patent applicant Daicel Chemical Industries, Ltd. ° 86

Claims (1)

[Claims] 1) An air sandwich type magneto-optical recording medium in which at least a magnetic recording layer is laminated on a substrate, characterized in that a vapor phase rust preventive agent is present in the space of the air sandwich. magneto-optical recording medium. 2) A magneto-optical recording medium characterized in that the vapor phase rust preventive agent shown in claim 1 is a nitrite.