JP2581983B2 - Optical recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium capable of recording, reproducing, and erasing by a light beam, and more particularly, to overwriting (overwriting) by a magnetic field modulation method. It concerns a possible optical recording medium.

2. Description of the Related Art Conventionally, a magneto-optical disk and its device capable of overwriting include, for example, JP-A-51-107121, JP-A-63-217548, JP-A-59-215008, Kimiaki
As described in Japanese Patent Application Laid-Open No. 60-48806 and the like, a method of modulating a magnetic field applied to a magneto-optical recording layer in accordance with information to be recorded, or a method of “Transaction on Magnetics (IEEE)” is used. Mag
Netics) MAG-20, Vol. 5, p. 1013 (1984), a method using two light spots is known.

Typical examples of conventional optical recording media having the above-mentioned magneto-optical recording layer include SiN, SiOx, ZnS, SiC and the like by vacuum evaporation, sputtering, etc. on a resin substrate having guide grooves and preformat signals. To form one or a combination of two or more inorganic dielectrics
An amorphous magneto-optical recording layer such as GdTb, TbFe, GdTbFe, TbFeCo, GdTbFeCo is provided, and a laminated film similar to the inorganic dielectric is formed on the magneto-optical recording layer, and an ultraviolet-curable acrylate is further formed thereon. A protective layer made of a resin composition is provided to protect the magneto-optical recording layer.

[Problems to be Solved by the Invention] In a magnetic field modulation type overwritable magneto-optical recording system using such an optical recording medium having a magneto-optical recording layer, a magnetic head and a magneto-optic Since the recording medium slides violently, a problem that the magnetic head frequently crashes occurs. Possible causes of the crash of the magnetic head include shavings of the magneto-optical recording medium caused by sliding, protrusions on the medium sliding surface, hardness, and the like.

Conventionally, as a countermeasure to prevent the crash of the magnetic head, a resin such as an ultraviolet-curable acrylate resin is applied to the side of the magneto-optical recording layer facing the magnetic head, for example, from 1 to
It has been proposed to provide a protective layer laminated to a thickness of 20 μm, but it is insufficient. Specifically, although a protective layer made of resin is provided on the magnetic disk, a CSS test (Con
Tact Start Stop Test) cannot clear 1,000,000 passes, causing a head crash.

That is, there is a problem that many resin protective layers such as conventional UV-curable acrylate resin compositions have poor sliding resistance.

The present invention has been made in order to solve such problems of the prior art, and by using an ultraviolet-curable resin composition containing a reactive silicone compound as a protective layer, lubrication of the surface of the protective layer can be achieved. It is an object of the present invention to provide an optical recording medium which has excellent slidability, good sliding resistance, no head crash, and can maintain long-term reliability.

[Means for Solving the Problems] That is, the present invention relates to an optical recording medium having at least a magneto-optical recording layer on a disk-shaped substrate, and a protective layer formed thereon. Is an optical recording medium comprising a UV-curable resin composition containing a reactive silicone compound.

 Hereinafter, the present invention will be described in detail.

The present inventor has conducted intensive studies in order to achieve the above object, and as a result, the cause of the crash of the magnetic head is as follows.
It has been found that the surface lubricity of the protective layer is insufficient.
Accordingly, the present invention provides an ultraviolet-curable resin containing a reactive silicone compound having excellent surface lubricity as compared with the above-mentioned conventional ultraviolet-curable acrylate-based resin composition in order to impart surface lubricity to the protective layer. It is characterized by using a composition.

In the present invention, as the ultraviolet-curable resin composition for forming the protective layer, a resin composition which is cured by irradiation with ultraviolet light which is generally used for the protective layer of an optical recording medium can be used without particular limitation. However, an ultraviolet curable acrylate resin composition is particularly preferred.

The UV-curable acrylate-based resin composition usually comprises a composition obtained by mixing (A) a prepolymer component, (B) a reactive diluent component, and (C) a photopolymerization initiator component. , (B) and (C)
(A) component 5 to 95%: (B) component 95 to 5% (weight ratio),
As the component (C), a composition incorporating 0.1 to 10% (weight ratio) is used. (A) As the prepolymer component, polyol polyacrylate, polyester acrylate,
Examples include urethane acrylate and epoxy acrylate. As the reactive diluent component (B), an acrylic acid ester of a polyhydric alcohol is used.
As the photopolymerization initiator component, known photopolymerization initiators are used, and those having good storage stability after blending are particularly preferable. Examples thereof include benzoin alkyl ethers, acetophenones, propiophenones, and anthraquinones. And thioxanthones. These are used alone or in combination of two or more at an arbitrary ratio.

Next, as the reactive silicone compound contained in the ultraviolet-curable resin composition, for example, one-terminal, both-terminal reactive silicone is used, and as the terminal functional group, a methacryloxy group that can be polymerized and cured by ultraviolet light is used. No. For example, a compound represented by the following formula (I) can be mentioned.

n = 1 to 131, Mw = 423 to 10,000 These reactive silicone compounds have their terminal functional groups polymerized and cured by ultraviolet rays. It is possible to impart lubricity to objects.

In addition, since the reactive silicone compound is incorporated in the three-dimensional polymer network in the cured resin, the lubricating property is excellent.

The amount of the reactive silicone compound added to the ultraviolet-curable resin composition is usually in the range of 2 to 15% by weight, and particularly preferably in the range of 5% to 10% by weight. 2 wt.
If the amount is less than 15% by weight, sufficient lubricating effect cannot be obtained. If the amount is more than 15% by weight, the curability due to the methacryloxy group is deteriorated, and the surface hardness is sometimes lowered.

The protective layer has a thickness of 2 to 30 μm, preferably 5 to 10 μm.
The range of μm is desirable. If it is less than 2 μm, the function of protecting the protective layer against scratches from the outside is not sufficient, and if it exceeds 30 μm, it is not preferable because the resin protective layer is peeled off by curing shrinkage.

The method for forming the protective layer in the present invention is, for example, by applying an ultraviolet-curable resin composition on the recording layer using a spin coater, a roll coater, a bar coater, or the like, and irradiating ultraviolet rays to cure the resin composition. Can be formed.

Further, the protective layer can be provided on one side or both sides of the optical recording medium.

In the optical recording medium of the present invention, the recording layer may be a magneto-optical recording layer or another type. For example, a recording layer using a dye may be used. Examples of the magneto-optical recording layer include amorphous magnetic recording layers such as GdTb, TbFe, GdTbFe, TbFeCo, and GdTbFeCo.

The substrate is not particularly limited, but a substrate made of, for example, a polycarbonate resin, an acrylic resin, a polystyrene resin, or a polyolefin resin having a guide groove and a preformat signal is used.

EXAMPLES Hereinafter, the present invention will be described more specifically by showing examples.

Embodiment I FIG. 1 is an explanatory view showing one embodiment of the optical recording medium of the present invention. An optical recording medium shown in FIG. First, an 800 mm thick Si ₃ N ₄ layer 2 is formed on a 1.2 mm thick polycarbonate substrate 1 having guide grooves and / or preformat signals by sputtering, and then a 400 mm thick amorphous GdTb layer is formed. Then, a magneto-optical recording layer 3 was provided by laminating amorphous TbFe having a thickness of 400 Å, and a Si ₃ N ₄ layer 4 having a thickness of 1000 Å was formed.

Next, a UV-curable urethane acrylate resin composition having the following composition was spin-coated (4000 rpm, 7 seconds) to form a resin layer having a thickness of 7 μm.
(3 W / cm ² , wavelength 365 nm) for 7 seconds to cure the resin and form a resin protective layer 5 to obtain an optical recording medium.

Composition (A) Caprolactone-modified dipentaerythritol hexaacrylate (6-functional) (trade name KAYARAD DPCA-3)
0, Nippon Kayaku Co., Ltd.) 80% by weight (B) Urethane acrylate (trade name ARONIX M
-1100) 10% by weight (C) Photopolymerization initiator (trade name: IRG-184, manufactured by Ciba-Geigy Japan) 5% by weight (D) Reactive silicone n (calculated value) = 10, Mw = 1000 (trade name: Sylaplane FM0711 manufactured by Chisso Corporation) 5
% By weight Example 2 (A) Caprolactone-modified dipentaerythritol hexaacrylate (6-functional) 75% by weight (D) Reactive silicone 10% by weight The optical recording medium was prepared in the same manner as in Example 1 except that the blending amounts were as follows. It was created.

Example 3 (A) Caprolactone-modified dipentaerythritol hexaacrylate (6-functional) 75% by weight (D) As reactive silicone, trade name: Sylaprene FM0711 manufactured by Chisso Corporation 3-methacryloxypropyltris (trimethylsiloxy) silane 10 wt% %, An optical recording medium was prepared in the same manner as in Example 1.

Example 4 (A) Caprolactone-modified dipentaerythritol hexaacrylate (6 functional groups) 80% by weight (D) As reactive silicone, n = 64, Mw = 5000, 5% by weight, trade name, manufactured by Sylaprene FM0711 Chisso Co., Ltd. Except for the above, an optical recording medium was prepared in the same manner as in Example 1.

Comparative Example 1 An optical recording medium was prepared in the same manner as in Example 1 except that (A) caprolactone-modified dipentaerythritol hexaacrylate (6 functional groups) was used at 85% by weight and (D) reactive silicone was not used.

As shown in FIG. 1, the medium is levitated and rotated at 3600 rpm for two seconds from the state where the flying magnetic head 6 is in contact with the surface of the medium, using each optical recording medium thus prepared. (The flying height of the magnetic head is 1.6 μm) After that, in 2 seconds, the rotation of the medium is reduced from 3600 rpm and stopped to bring the magnetic head into contact with the medium surface. As a result of repeating the CSS test, Examples 1 to 4 were able to clear the CSS test of 1,000,000 passes and no head crash occurred. On the other hand, Comparative Example 1
A 1 million pass CSS test failed and a head crash occurred.

That is, according to the present invention, it is possible to achieve a magneto-optical disk drive system that maintains reliability for a long time.

[Effects of the Invention] As described above, according to the optical recording medium of the present invention, by using an ultraviolet-curable resin composition containing a reactive silicone compound as the protective layer, the lubricity of the protective layer is excellent. Good sliding resistance, no head crash, and long-term reliability can be maintained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the optical recording medium of the present invention. 1 ...... substrate, 2, 4 ...... Si ₃ N ₄ layer 3 ...... magneto-optical recording layer, 5 ...... protective layer 6 ...... floating magnetic head

Claims (1)

(57) [Claims] 1. An optical recording medium comprising a disc-shaped substrate having at least a magneto-optical recording layer on which a protective layer is formed, wherein the protective layer contains a reactive silicone compound. An optical recording medium comprising a mold resin composition.