JP2619450B2 - Magneto-optical disk - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk, and particularly to a magnetic recording disk, which has good contact with a recording film, and is capable of preventing head contact during overwrite recording by a magnetic field modulation method. And a magneto-optical disk protective film structure suitable for forming a hard and strong protective film.

[Conventional technology]

As a conventional method for protecting the recording film surface of a magneto-optical disk, as described in U.S. Pat. No. 4,310,919, there has been a method in which another type of substrate is overlaid with an adhesive, but in this method, a production method is used. There is a problem that it is not possible to improve the performance and reduce the cost. Also, overwrite recording by a magnetic field modulation method is impossible.

Therefore, as described in Utility Model No. 61-153129, a method of covering the surface of a substrate having a recording film with a single-layer or multilayer light-transmitting resin film has recently been implemented.

[Problems to be solved by the invention]

The prior art described above does not consider the fact that a protective film having good adhesion to the recording film and a hard surface is formed, and the magnetic field generated when performing overwrite recording by the magnetic field modulation method is not considered. Considering the contact of the head with the protective film, it was insufficient as a high-quality magneto-optical disc capable of stable recording and reproduction.

SUMMARY OF THE INVENTION It is an object of the present invention to form a resin having high adhesion to a recording film and a high surface hardness on a magneto-optical disk.

[Means for solving the problem]

The above-mentioned object is to form a protective film made of a resin into a single layer or a multilayer, and form a resin having good adhesiveness with the recording film on a surface or a layer in contact with the recording film, and on the protective film surface or the outermost layer,
This is achieved by forming a hard resin.

[Action]

When a powder made of an inorganic material is mixed into a resin used as a protective film and left for several minutes, the powder sediments by its own weight.
Therefore, on the recording film surface of a magneto-optical disc having a recording film,
When a mixture of a resin and an inorganic powder having good adhesiveness to the recording film is applied, and the mixture is turned upside down and left to stand, the powder is deposited on the lower layer of the resin layer (outer layer of the protective film). As a result, the protective film is separated into two layers, and a layer having good adhesiveness is formed on the recording film side, and a hard layer is formed on the surface of the protective film by powder made of an inorganic substance.

On the other hand, a resin having good adhesiveness with the recording film is first applied on the substrate having the recording film and semi-cured. Next, when a hard resin having another hardness is further applied and further cured, the semi-cured resin and the resin having a high surface hardness can be adhered with good adhesion, and the adhesion with the recording film is also good.

The magneto-optical disk manufactured by the above method has a structure as shown in FIG. 1A, and the relationship between the position of the thickness of the recording film and the hardness (measured by a Vickers hardness meter) is as shown in FIG. 1B. It has become.

In addition, this disk can be used at high temperature (60 ° C or higher), high humidity (95%
% Or more), no separation from the recording film occurs, and damage to the protective film can be prevented even when the magnetic head comes into contact with the protective film when performing overwrite recording by the magnetic field modulation method. As a result, stable recording and reproduction can be performed.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Example 1 As shown in FIG. 2, a powder (SiO) made of an ultraviolet curable resin having good adhesiveness to a recording film previously prepared and an inorganic material was applied to a transparent, flat, and highly releasable stamper 8. ₂ etc.)
Is applied concentrically. Next, the substrate 1 having the recording film 2 in an information pattern is overlaid so that the film surface faces downward so that bubbles do not enter, and a weight of 10 kg or more is applied from the back side of the substrate 1 to homogenize the mixture 4 previously. And spread it out. After removing the excess mixture 4 protruding from the base 1, the mixture 4 is left for several minutes until the inorganic powder in the mixture 4 sediments by its own weight.

Thereafter, the mixture 4 is cured by irradiating ultraviolet rays 9 from the stamper 8 side, and the stamper 8 is removed. The magneto-optical disk manufactured in this way has a very hard protective film surface,
In addition, it has excellent adhesiveness. As a result of testing under high temperature (60 ° C. or more) and high humidity (95%) or more environment, the life of the protective film that has been peeled off from the recording film in several weeks is more than several months. Could be extended.

As the inorganic powder, in addition to SiO ₂ , Al ₂ O ₃ .C
An oxide such as r ₂ O ₃ .ZrO _2, a nitride such as Si ₃ N ₄ .BN, and a carbide such as SiC can harden the protective film in the same manner as the above-described effect.

At the same time, a method of applying a mixture of an ultraviolet curable resin and an inorganic powder can also be applied by spin coating using a spinner in addition to the above.

Example 2 As shown in FIG. 3, the substrate 1 having the recording film 2 is mounted on a turntable 10, and an ultraviolet curable resin 5 having good adhesion to the recording film is spin-coated uniformly. After confirming that dust and impurities do not adhere to the surface, ultraviolet rays 9 are irradiated. At this time, the irradiation time of the ultraviolet rays 9 is set within a range of half or less (for example, 1 to 5 seconds) of the curing of the resin, and the resin 5 is in a semi-cured state. Next, the base 1 with the resin 5 is again attached to the turntable 11.
And apply a high hardness resin 6 by spin coating on the resin 5 and confirm that there is no foreign matter.
Irradiate for 30 seconds. Thereby, the adhesiveness between the lower resin 5 and the upper resin 6 is strengthened, and peeling between the two layers does not occur. In the case where three or four layers are continuously stacked, it is sufficient to irradiate ultraviolet rays for 30 seconds or more only when curing the resin of the outermost layer. The irradiation time of the other layers is within 1 to 5 seconds.

[Embodiment 3] In the embodiment shown in FIGS. 2 and 3, the resin of the protective film material is limited to the ultraviolet curable resin, but it is also possible to use the thermosetting resin or the anaerobic resin 7 for production. . Also, the fourth
As shown in the figure, in the case of a multilayer, a combination of an ultraviolet curable resin and a thermosetting resin or an anaerobic resin 7 is also effective.

FIG. 1 (b) shows the results obtained by measuring the hardness of the protective film produced by the above method with respect to the thickness position using a Vickers hardness tester. This shows that the hardness at the place having a thickness of about 10 μm from the outermost layer is harder than that of the inner layer part, and the hardness is about 500 g / cm ² .

〔The invention's effect〕

According to the present invention, a protective film having a high surface hardness and good adhesion to a recording film can be formed on a magneto-optical disk substrate, so that a high-quality magneto-optical disk capable of performing stable recording and reproduction can be obtained. effective.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (a) is a cross-sectional view of a magneto-optical disk structure of the present invention, and FIG. 1 (b) shows hardness corresponding to a position in a thickness direction of a protective film. is there. FIG. 2 is a cross-sectional view showing a first embodiment of the present invention, and FIG. 3 is a cross-sectional view showing a step of forming a magneto-optical disk protective film according to a second embodiment of the present invention. FIG. 4 is a sectional view showing a magneto-optical disc structure according to a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Recording film, 3 ... Protective film (single / multilayer structure), 4 ... Mixture of powder composed of an ultraviolet curable resin and an inorganic substance, 5 ... Resin having good adhesion to the recording film, 6: Hard resin, 7: Thermosetting resin or anaerobic resin, 8
…… Stamper, 9… Ultraviolet, 10… Turn table.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yumiko Ansai 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-63-302447 (JP, A)

Claims (3)

(57) [Claims] 1. A magneto-optical disk having a single-layer or multilayer resin film on a substrate having a recording film and covering the surface of the recording film, opposite to the first surface of the resin film in contact with the recording film. A second surface on the side having a high hardness, wherein the resin on the second surface is mixed with an inorganic material. 2. The resin film has a first layer in contact with the recording film and a second layer exposed on the surface of the magneto-optical disk, and the resin constituting the second layer contains an inorganic powder. 2. The magneto-optical disk according to claim 1, wherein the magneto-optical disk is mixed. 3. The magneto-optical disk according to claim 1, wherein said inorganic substance is an oxide, nitride, or carbide powder of metal or silicon.