JPH06195779A - Magneto-optic recording medium - Google Patents

Abstract

PURPOSE:To improve the characteristics of a magneto-optic recording medium under a contact state with a floating head, and to lengthen life by dispersing a metal oxide from 50 to 500Angstrom and imparting conductivity in an organic-resin protective layer. CONSTITUTION:A magneto-optic recording medium is constituted while including a recording layer 2 and an organic-resin protective layer 3 successively laminated on a substrate 1. Metal oxide particles 4 from particle size of 50 to 500Angstrom are dispersed in the protective layer 3, thus forming fine projections 3a in the surface of the protective layer 3. Accordingly, a floating magnetic head and the protective layer 3 are not fast stuck, thus preventing the attraction of both the head and the protective layer while reducing friction at the time of a contact. Conductivity is imparted to the oxide particles 4, thus effectively obviating the charging of the surface, then also eliminating an accident, in which dust is bitten between the head and the medium during floating. Consequently, the characteristics of the medium can be improved under the contact state of the floating head and the magneto-optic medium, thus lengthening both life of the head and the medium.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a magneto-optical recording medium. More specifically, the present invention relates to a magneto-optical recording medium capable of recording / reproducing information by a laser beam, and in particular, a magneto-optical recording / reproducing apparatus of a magnetic field modulation type using a flying magnetic head. The present invention relates to a new structure of a recording medium.

[0002]

2. Description of the Related Art Information recording processing on a magneto-optical recording medium is performed in three steps of erasing, writing and verifying. Therefore, compared with other information recording media such as magnetic recording media, the time required for the information recording process is long, which is a major problem in practical use.

In order to solve such a problem, according to the magnetic field modulation overwrite method which has been recently developed, the recording process can be completed only by the writing and verifying processes while omitting the erasing process. That is, in this method, the time required for the recording process on the magneto-optical recording medium can be shortened to 2/3.

By the way, in the magnetic field modulation overwrite system, many drive devices use a flying head slider which is a dynamic pressure gas bearing. The flying head is configured to fly above a magneto-optical recording medium that rotates at a high speed with a minute gap, and the head applies a magnetic field to the medium in a non-contact state. When the flying head contacts the surface of the medium in this manner, either the head or the medium surface is damaged.

Generally, in a magneto-optical recording medium, a height difference is likely to be formed on the surface of the organic resin protective layer formed at the end of the manufacturing process due to uneven coating on the surface, mixing of foreign matters, splashing of the coating resin, and the like. However, the flying magnetic head used in the magnetic field modulation overwrite method faces the organic resin protective layer side, and contact travel easily occurs due to a rapid change in the gap with the medium.

Further, in a drive device using a flying head, the head is generally in contact with the medium during rest and is stationary, and when the device starts and the rotation of the medium reaches a predetermined speed, the head is stopped. Surface. Also, when the apparatus stops and the medium stops rotating, the head rests again on the medium. Such a method is called a contact start stop (hereinafter referred to as "CSS") method, and the magnetic field modulation overwrite method has become a mainstream configuration. That is, in this CSS method, the flying head is in contact with the medium and runs until the rotation of the medium reaches a predetermined speed.

Further, in the case of the CSS system, the head is stationary on the medium when stopped as described above. here,
The surface of the medium is generally smooth, and the head may be attracted to the medium when the stop time is long. In such a case, an excessive external force is applied to the head when the drive device is started up, which causes damage such as peeling of the head.

As described above, the floating magnetic head and the magneto-optical recording medium come into contact with each other in various states as described above, but generally the surface of the magneto-optical recording medium is not manufactured in consideration of lubricity. If the contact travel time and the number of times increase, the wear and damage of the flying magnetic head or the magneto-optical recording medium cannot be ignored.

[0009]

Therefore, the present invention aims to solve the above-mentioned problems of the prior art, improve the characteristics of the magneto-optical recording medium in contact with the flying head, and prolong the life of both. Its purpose is.

[0010]

According to the present invention, there is provided a transparent substrate, a recording layer loaded on the transparent substrate and an organic resin protective layer, and the recording layer is irradiated by a light beam radiated through the substrate. In a magneto-optical recording medium used in a magnetic field modulation method capable of recording, reproducing and erasing information, the organic resin protective layer is characterized by including metal oxide particles having a particle size of 50Å to 500Å Media is provided.

According to a preferred embodiment of the present invention,
In the magneto-optical recording medium according to the present invention, the metal oxide particles have conductivity.

Furthermore, in the magneto-optical recording medium according to the present invention, the content of the metal oxide particles is 10% by weight to 70% by weight.
It is preferably in the weight%.

[0013]

The main feature of the magneto-optical recording medium of the present invention is that the organic resin protective layer contains metal oxide particles having a particle size of 50Å to 500Å.

In the conventional magneto-optical recording medium, no special consideration was given to the characteristics of the surface of the organic resin protective layer.
On the other hand, the magneto-optical recording medium according to the present invention is a magneto-optical recording medium in consideration of adsorption to the head at rest, contact traveling at startup, and contact with the traveling head due to an accidental cause. The surface properties of the recording medium are improved.

That is, in the magneto-optical recording medium according to the present invention, the metal oxide particles are dispersed in the organic resin protective layer, whereby many minute projections are formed on the surface of the organic resin protective layer. . Therefore, the head and the surface of the medium do not come into close contact with each other when stationary, and the head is not attracted.
Further, friction during contact traveling is also reduced. Therefore, an excessive force does not act on the head due to adsorption or contact between the medium and the head.

Further, according to one aspect of the present invention, the metal oxide particles have conductivity. Therefore, the surface of the medium is not charged, and dust or the like is not sucked by the charging of the medium. That is, when the organic resin protective layer is charged with static electricity, foreign matter such as dust easily adheres, and this foreign matter is trapped between the floating magnetic head and the magneto-optical medium, which causes It has been one of the major causes of damage to the recording medium or the flying magnetic head. On the other hand, in the magneto-optical recording medium according to the present invention, charging of the medium is prevented by the above-mentioned configuration, and the damage to the head and the medium during running is significantly reduced.

The particle size of the metal oxide particles dispersed in the organic resin protective layer is in the range of 50Å to 500Å. The reason is that if the particle size is smaller than the above range, the undulations formed on the surface of the organic resin protective layer are too small to obtain the desired effect. On the other hand, if the particle size is larger than the above range, the protruding portion formed on the surface of the organic resin protective layer becomes too large and the flying of the magnetic head becomes unstable.

The content of metal oxide particles in the organic resin protective layer is preferably in the range of 10% by weight to 70% by weight. The reason is that if the content is less than the above range, the number of protruding portions formed on the surface of the organic resin protective layer is small, and a completely flat region is generated, so that the desired effect is not always obtained. Is not obtained. On the other hand, when the content is larger than the above range, the surface property of the organic resin protective layer becomes extremely rough and the friction with the head becomes rather large. Further, when an ultraviolet curable resin is used for the organic resin protective layer, there is a problem that the metal oxide particles block ultraviolet rays and the resin is hard to cure.

Further, as the material of the metal oxide particles,
Examples thereof include indium oxide, tin oxide, antimony oxide and the like. These materials are electrically conductive and, since fine particles can be easily obtained, they are easy to use. However, it goes without saying that the present invention is not limited to this material.

Hereinafter, the present invention will be described more specifically with reference to specific examples, but the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention.

[0021]

1 is a diagram schematically showing the structure of a magneto-optical recording medium according to the present invention.

As shown in the figure, this magneto-optical recording medium comprises a recording layer 2 and an organic resin protective layer 3 which are sequentially laminated on a substrate 1. Furthermore, in the organic resin protective layer 3, metal oxide particles 4 having a particle size of 50Å to 500Å are dispersed. Therefore, minute protrusions 3a are formed on the surface of the organic resin protective layer 3.

Here, as a specific material of the substrate 1, a transparent plastic material such as a polyolefin resin, which is cost-effective, can be exemplified, but glass or the like can be used.

The recording layer 2 can be formed of, for example, a pair of inorganic dielectric films for preventing oxidation and an alloy film sandwiched between the inorganic dielectric films. Specific materials for the inorganic dielectric film include SiO, SiO ₂ , Si ₃ N ₄ , and Al ₂ O.
₃ etc. can be illustrated. Further, as a specific material of the alloy film, an alloy such as Gd, Tb, Fe and Co can be exemplified.

Specific examples of the material of the organic resin protective layer 3 include photocurable resin, hot melt resin, epoxy resin, UV curable resin and the like.

In the magneto-optical recording medium having the above structure, as shown in FIG. 1, fine projections are formed on the surface of the organic resin protective layer 3 by the metal oxide particles. Therefore, the floating magnetic head and the organic resin protective layer do not come into close contact with each other, so that both are prevented from adsorbing and friction at the time of contact is reduced.

Further, since the metal oxide particles 4 can be provided with conductivity, the surface of the magneto-optical recording medium can be effectively prevented from being charged. Therefore, it is possible to effectively prevent an accident in which dust is caught between the flying head and the medium.

In the above magneto-optical recording medium, a reflective layer may be formed between the recording layer 2 and the organic resin protective layer 3 by using Al or Au.

Although FIG. 1 is intended for a so-called disk-shaped medium, the present invention is not limited to this and is also effective for a card-shaped or drum-shaped medium.

[Manufacturing Example 1] A magneto-optical recording medium according to the present invention was actually manufactured using a polycarbonate resin spiral grooved substrate having a diameter of 86 mm. First, SiN, TbFeCo, SiN and Al are sequentially deposited in this order as an inorganic dielectric film, a recording film, an inorganic dielectric film and a reflective film on the grooved surface of the substrate by the RF magnetron sputtering method. It was Subsequently, an ultraviolet curable resin as an organic resin protective layer was applied on the uppermost reflective layer by spin coating. The UV curable resin used here was SD301 manufactured by Dainippon Ink and Chemicals, Inc., in which 70 wt% of indium oxide particles having a particle size of 200Å were dispersed. A resin having such a component was applied to a thickness of 5 μm and cured by irradiation with ultraviolet rays to complete a magneto-optical recording medium.

The center line flatness of the obtained magneto-optical recording medium with an uneven surface, the CSS durability test, and the antistatic function were measured.

In the CSS endurance test, the magneto-optical recording medium is mounted on the CSS tester, the CSS (contact start stop) operation of the flying head is repeated, and the number of times until the head scratches the disk surface is measured. The durability was evaluated. The evaluation results are shown in Table 1.

Comparative Example 1 An organic resin protective layer was coated with SD301 manufactured by Dainippon Ink and Chemicals Co., Ltd. having a thickness of 5 μm in which 70% by weight of indium oxide particles having an average particle diameter of 500Å were dispersed, and then irradiated with ultraviolet rays. Then, it was cured to prepare a magneto-optical recording medium. In other respects, a magneto-optical recording medium was manufactured using the same materials and conditions as in Manufacturing Example 1. With respect to the obtained Comparative Example 1, the measurement of the center line average roughness and the
S durability and antistatic performance were evaluated. The evaluation results are also shown in Table 1.

[Comparative Example 2] An organic resin protective layer having a particle size of 20
A magneto-optical recording medium was prepared by applying SD301 manufactured by Dainippon Ink and Chemicals Co., Ltd. having a thickness of 5 μm, in which 70% by weight of indium oxide particles smaller than Å were dispersed, and then curing by UV irradiation. In other respects, a magneto-optical recording medium was manufactured using the same materials and conditions as in Manufacturing Example 1. Obtained Comparative Example 2
For the sample of No. 3, the center line average roughness was measured and the CSS durability and antistatic performance were evaluated in the same manner as in Preparation Example 1. The evaluation results are also shown in Table 1.

Comparative Example 3 SD301 manufactured by Dainippon Ink and Chemicals Co., Ltd., in which 70% by weight of indium oxide particles having an average particle diameter of 1000 Å are dispersed, is applied to the organic resin protective layer to a thickness of 5 μm, and then UV irradiation is performed. Then, it was cured to prepare a magneto-optical recording medium. In other respects, a magneto-optical recording medium was manufactured using the same materials and conditions as in Manufacturing Example 1. With respect to the obtained sample of Comparative Example 3, the center line average roughness was measured and the CSS durability and the antistatic performance were evaluated in the same manner as in Production Example 1.
The evaluation results are also shown in Table 1.

[Comparative Example 4] A magneto-optical recording medium was manufactured using exactly the same materials as in Manufacturing Example 1 and under the same manufacturing conditions. However,
Indium oxide content in UV curable resin is 10
It was set to% by weight. The obtained sample of Comparative Example 4 was evaluated for center line average roughness, CSS durability and antistatic performance in the same manner as in Production Example 1. The evaluation results are also shown in Table 1.

Comparative Example 5 A magneto-optical recording medium was manufactured using the same materials as in Manufacturing Example 1 and under the same manufacturing conditions. However,
The content ratio of indium oxide to the UV curable resin is 5
It was set to% by weight. The obtained sample of Comparative Example 5 was evaluated for center line average roughness, CSS durability and antistatic performance in the same manner as in Production Example 1. The evaluation results are also shown in Table 1.

[Comparative Example 6] A magneto-optical recording medium was manufactured by using the same materials as in Manufacturing Example 1 and under the same manufacturing conditions. However,
The ultraviolet curable resin did not contain indium oxide at all. For the obtained sample of Comparative Example 6, the center line average roughness was measured and the CSS durability and the antistatic performance were evaluated in the same manner as in Production Example 1. The evaluation results are also shown in Table 1.

[0039]

[Table 1]

As can be seen from Table 1, the magneto-optical recording medium having the organic resin protective layer containing metal oxide particles has a remarkable CSS test result as compared with the magneto-optical recording medium having the conventional structure (Comparative Example 6). Is excellent. Further, the metal oxide particles contained in the f-season particle size and content have more excellent characteristics among them.

[0041]

As described above, in the magneto-optical recording medium according to the present invention, the surface of the organic resin protective layer has a low friction property and a low adsorption property, and a drive device having a flying magnetic head. The damage due to traveling with the head and the adsorption at rest are significantly reduced.

By making the metal oxide particles dispersed in the organic resin protective layer conductive, the medium is not charged and dust is not attracted. Therefore, accidents such as dust entrapment during operation are reduced.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a configuration of a magneto-optical recording medium according to the present invention.

[Explanation of symbols]

 1 ... Substrate, 2 ... Recording layer, 3 ... Organic resin protective layer, 4 ... Metal oxide particles

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Takatsuka 1239 Shinjae, Aboshi-ku, Himeji-shi, Hyogo, Daicel Chemical Industry Co., Ltd. Inside the research institute

Claims (4)

[Claims] 1. A transparent substrate, a recording layer and an organic resin protective layer loaded on the transparent substrate, and information can be recorded, reproduced, and erased on the recording layer by a light beam irradiated through the substrate. A magneto-optical recording medium used in a magnetic field modulation method, wherein the organic resin protective layer contains metal oxide particles having a particle diameter of 50Å to 500Å. 2. The magneto-optical recording medium according to claim 1, wherein the metal oxide particles have conductivity. 3. The magneto-optical recording medium according to claim 1, wherein the content of the metal oxide particles is 10% by weight to 70% by weight. Magnetic recording medium. 4. The magneto-optical recording medium according to any one of claims 1 to 3, wherein the metal oxide particles are at least one selected from indium oxide, tin oxide and antimony oxide. A magneto-optical recording medium comprising the metal oxide particles of