JP2600710B2 - Magneto-optical disk and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a magneto-optical disk for recording a large amount of information at a high speed, and aims at practical use of a magneto-optical disk capable of overwriting signals. The magneto-optical disk is formed on a disk-shaped substrate. A second layer comprising a base film, a recording film, and a protective film laminated on the first substrate, and a lubricant that has reacted with the uncured reaction resin of the thermosetting resin in the thermosetting resin on the protective film. The method for manufacturing a magneto-optical disk is such that a base film, a recording film, and a protective film are formed in layers on a disk-shaped substrate. A step of applying a mixed liquid of a thermosetting resin and a material not involved in the curing reaction of the thermosetting resin on the film, and baking at a temperature lower than a baking temperature at which the thermosetting resin is completely cured; And extracting the irrelevant material, and Impregnating a lubricant having a reactive group with the uncured reaction resin to form a second protective film.

[Industrial applications]

The present invention relates to a magneto-optical disk capable of overwriting signals.

The magneto-optical disk is made of a magnetic film whose recording film is perpendicularly magnetized, and when a laser beam is irradiated from the outside while applying a perpendicular magnetic field in the direction opposite to the magnetization direction, the coercive force decreases due to the temperature rise of the irradiated magnetic film. This is a memory for recording and erasing information by utilizing magnetization reversal.

The reproduction of information is performed by utilizing the fact that the polarization plane of the reflected light rotates when the magnetic film is irradiated with the laser light, and the rotation direction differs depending on the magnetization direction of the magnetic film.

The present invention relates to an improvement of such a magneto-optical disk.

[Conventional technology]

In the conventional magneto-optical disk device, the application of a magnetic field is performed using an electromagnet.However, the distance between the recording film for recording information and the electromagnet is as large as about 5 mm, which differs depending on the magnetic material constituting the recording film. In order to apply a magnetic field of a degree to the recording film, a considerable amount of current and inductance are required.

Therefore, it takes time to invert the magnetic field, and high-speed recording at several MHz cannot be performed.

For this reason, when rewriting information on the magneto-optical disk, it is necessary to erase information at a required position and then wait for one rotation before recording.

On the other hand, recording, reproducing, and erasing of information on the magnetic disk is performed using a magnetic head that floats at a very small interval of about 0.2 μm due to the lift caused by the high-speed rotation of the magnetic disk. Therefore, high-speed reversal of the magnetic field is possible, and overwriting is possible.

The present inventors have proposed that a magnetic field be applied using a magnetic head for a magnetic disk in order to enable overwriting on a magneto-optical disk, and have promoted its practical use, but in this case, there is a problem. Head crash.

In other words, the magnetic head floats over a minute gap due to the lift generated by the high-speed rotation of the disk. This causes damage to the recording film.

For this purpose, the magnetic film of the magnetic disk is formed with a strength that can withstand a head crash.

Now, the inventors have proposed that a second protective film is further provided on the conventional protective film as a method for making the magneto-optical disk resistant to head crash.

FIG. 1 is a cross-sectional structural view showing this structure, in which glass or a synthetic resin [for example, polymethyl methacrylate (abbreviated as PM
MA), polycarbonate (abbreviated PC)], a conventional magneto-optical disk is formed by forming a base film 2, a recording film 3, and a first protective film 4 on a transparent substrate 1 made of The structure proposed by the present inventors is to provide a second protective film 5 for head crash resistance on this.

Here, the underlayer 2 prevents moisture and oxygen from penetrating through the transparent substrate 1 and is formed of a transparent and dense insulating film such as silicon nitride (Si ₃ N ₄ ), and the recording film 3 is terbium. A perpendicular magnetic film made of a rare earth / transition metal alloy such as iron / cobalt (TbFeCo), and a first protective film 4 for preventing the recording film 3 from being deteriorated by moisture absorption or oxidation; It is formed of an insulating film similar to the base film 2.

Now, the requirement of the second protective film is that the mechanical strength is excellent,
And it is smooth and has a low coefficient of friction.

As a second protective film, the present inventors have made a thermosetting resin containing alumina powder impregnated with a lubricant, a magnetic coating film impregnated with a lubricant, and a coating film made of a thermosetting resin. We have researched about the surface impregnated with lubricant with small holes (pores) interspersed with it, but the mechanical strength is excellent. Lubricant gradually consumed due to evaporation during use. In addition, it is not possible to maintain the lubricity of the surface of the magneto-optical disk for a long period of time due to the movement of the magneto-optical disk over a long period of time due to the centrifugal force.

[Problems to be solved by the invention]

As described above, when a magnetic field is applied to a magneto-optical disk using a magnetic head, it is necessary to adopt a structure that can withstand a head crash, and a second protective film for head crash is provided on a conventional protective film. However, it is a problem that the lubricity of the surface cannot be maintained for a long period of time.

[Means for solving the problem]

The above problem has a base film, a recording film, and a protective film laminated on a disk-shaped substrate, and the thermosetting resin is uncured on the protective film in a thermosetting resin. The problem is solved by a magneto-optical disk configured so that a second protective film containing a lubricant reacted with a reactive resin is applied.

In addition, a base film, a recording film, and a protective film are formed in layers on a disk-shaped substrate, and a thermosetting resin and a material not involved in a curing reaction of the thermosetting resin are formed on the protective film. Applying a mixed solution of the above, baking at a temperature lower than the baking temperature at which the thermosetting resin is completely cured to leave uncured reaction resin, and extracting the unrelated material, and And forming a second protective film by impregnating with a lubricant having the following properties to react with the uncured reaction resin.

[Action]

The present invention has further developed "the one in which small holes (pores) are scattered on the surface of a coating film made of a thermosetting resin and impregnated with a lubricant" described above in the section of "prior art". Things.

In other words, specifically speaking, in the prior art, a thermosetting resin such as phenol and a material such as paraffin not involved in the thermosetting reaction are mixed using a solvent to form a coating liquid, which is then subjected to magneto-optical After coating on the first protective film of the disk to form a coating film, the film is heated to polymerize and cure the thermosetting resin (in this case, phenol).

Next, many small holes (pores) are made in the surface by extracting a material (in this case, paraffin) that does not participate in the thermosetting reaction using a solvent, and a lubricant such as fluorocarbon oil is applied to the holes. It is made to fill.

However, these lubricants gradually migrate and wear away simply because they are filled in the pores, and thus the lubricity is reduced.

Therefore, the present invention is to react the thermosetting resin with the lubricant and fix the resin to the surface of the resin containing pores.

That is, when heating and curing a coating film formed by mixing a thermosetting resin (for example, epoxy resin) with a material (for example, paraffin) that does not participate in the thermosetting reaction, baking is performed at a temperature equal to or lower than a baking temperature at which complete curing is performed. By removing the paraffin using a solvent, a resin layer 7 having a functional group on the surface and having pores 6 is formed as shown in FIG. 1 (B), while a lubricant 8 having a reactive group is used. After application and impregnation, the resin is heated and reacted at a temperature at which the resin is completely cured to obtain a second protective film 5 in which the two are fixed.

By adopting such a method, it is possible to solve the problem that the lubricant is gradually consumed as in the related art.

〔Example〕

A coating liquid having the composition shown in Table 1 was prepared as a coating liquid for forming the second protective film.

Next, a fluorocarbon oil derivative having the following structural formula was used as a lubricant having a reactive group.

As a magneto-optical disk, a transparent substrate 1 having a guide groove (pre-groove) provided by covering PMMA to a thickness of 30 μm on a glass substrate having a thickness of 1.2 mm in FIG. On this, a zinc sulfide (ZnS) film is formed to a thickness of 85 nm, a base film 2 is formed, a TbFeCo film is formed to a thickness of 90 nm, a recording film 3 is formed, and a ZnS film is formed to a thickness of 85 nm. Was formed to form a first protective film 4 to produce a magneto-optical disk having a conventional structure.

Next, a coating liquid having the composition shown in Table 1 was spin-coated on the magneto-optical disk having the conventional structure to form a 0.5 μm coating film, which was then cured by heating at 100 ° C. for 1 hour.

As shown in FIG. 2, the temperature of 100 ° C. is a condition under which the curing of the epoxy-phenol-based resin proceeds by 80%, and contains 20% of unreacted components.

The pores were formed by wiping the resulting resin layer with a cloth impregnated with toluene while rotating.

Next, as described above, a fluorocarbon oil having a carbosyl group (—COOH) at the terminal is applied to this resin layer,
The reaction was carried out by heating at 0 ° C. for 1 hour and the resin was completely cured.

By using such a method, the lubricant could be fixed to the resin layer.

The magneto-optical disk according to the present invention manufactured by the method described in the embodiment was rotated at a rotation speed of 10,000 r.
After rotating for 700 hours under the condition of pm, a contact head stop (abbreviated CSS) test was performed with the magnetic head installed, but there was no change up to 100,000 times.

It was noted that a crash occurred from 30,000 times on a magneto-optical disk in which only the pores of the second protective film were filled with fluorocarbon oil as in the prior art.

〔The invention's effect〕

As described above, the lubricant of the present invention does not gradually dissipate and be consumed during use by the implementation of the present invention, so that the lubricity of the surface can be maintained, thereby applying a magnetic field using the magnetic head. In addition, a magneto-optical disk capable of overwriting signals can be put to practical use.

[Brief description of the drawings]

1 (A) is a sectional structural view of a magneto-optical disk according to the present invention, FIG. 1 (B) is an enlarged sectional view of a second protective film according to the present invention, and FIG. FIG. In the figure, 1 is a transparent substrate, 2 is a base film, 3 is a recording film, 4 is a first protective film, 5 is a second protective film, 6 is a pore, 7 is a resin layer, and 8 is a lubricant. .

Claims (2)

(57) [Claims] 1. A thermosetting resin comprising a base film, a recording film, and a protective film laminated on a disk-shaped substrate, wherein the thermosetting resin is uncured on the protective film. A magneto-optical disk, wherein a second protective film containing a lubricant reacted with a reactive resin is applied. 2. A method for manufacturing a magneto-optical disk in which a base film, a recording film, and a protective film are formed in a layer on a disk-shaped substrate, wherein a thermosetting resin and the thermosetting resin are provided on the protective film. Applying a liquid mixture with a material that is not involved in the curing reaction, baking at a temperature lower than the baking temperature at which the thermosetting resin is completely cured, and leaving an uncured reaction resin; and Extracted, impregnated with a lubricant having a reactive group in the resulting hole, reacted with the uncured reaction resin,
Forming a protective film according to (1).