JP2002042391A - Magneto-optic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field-modulation type magneto-optic recording medium, the protection layer of which is prevented from being worn out or damaged by the sliding motion of a magnetic head slider and the protection layer due to high-density recording in future and which is superior in durability even under the high-density recording condition. SOLUTION: This magneto-optical recording medium has a substrate 1, a protective layer 6 having unevenness on the surface and a magneto-optic recording layer 3 interposed between the substrate 1 and the layer 6. Such a lubricant layer 7 is arranged on the layer 6, that contains the monoester, obtained from unsaturated alkyl carboxylic acid and fluorinated alcohol. The uneven in height are in the range of >=0.05 μm to <=1 μm, the number of uneven points on the layer 6 is in the range of >=1 piece/μm2 to <=20 pieces/μm2, and the thickness of the layer 7 is in the range of 50 nm to 200 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium capable of recording, reproducing, and erasing with a light beam, and more particularly to a magneto-optical recording medium capable of overwriting by a magnetic field modulation method.

[0002]

2. Description of the Related Art In recent years, magneto-optical recording media have attracted attention as optical recording media capable of rewriting recorded contents. further,
The overwritable magneto-optical recording medium and reproducing apparatus which do not need to erase old contents prior to rewriting of recorded contents have become mainstream. These are disclosed in
Nos. 9-215008, JP-A-60-48806 and JP-A-63-217548. In this method, a magnetic coil and a core are provided on a magnetic head slider in order to overwrite the magneto-optical recording medium, and the magnetic coil and the core are disposed so as to face a protective layer of the rotating magneto-optical recording medium. The magnetic head slider is levitated above the magneto-optical recording medium by the airflow generated during the period. For this reason, the magnetic head slider does not come into contact with the magneto-optical recording medium due to the action of airflow at a predetermined rotation speed.
However, at the start or end of driving, the magnetic head slider loses levitation force due to a decrease in the number of revolutions, and comes into direct contact with the magneto-optical recording medium. As a result, the magneto-optical recording medium may be worn and damage the magneto-optical recording layer.

In order to solve such a problem, various proposals have been made for a protective layer of a magneto-optical recording medium. For example, JP-A-2-301040, JP-A-2-301
No. 041 proposes that a fluorine-containing polyurethane resin be used as a main component, and JP-A-3-37844 proposes that a fluorine resin that is soluble in an organic solvent is used as a main component. Further, JP-A-2-40149 discloses that
It has been proposed to use a protective layer in which a lubricant is mixed into an ultraviolet curable resin. Japanese Patent Application Laid-Open No. Hei 3-62338 discloses that unevenness of 0.1 μm to 0.5 μm is uniformly present on the surface of the protective layer. Proposed.

[0004]

However, with the above-described method, it is possible to prevent the friction and the wear due to the temporary sliding at the time of driving and termination, but it is possible to prevent the magnetic head slider by high density recording in the future. It has been impossible to manage severe sliding such as constant contact of the magnetic recording medium and always prevent friction and wear of the magneto-optical recording medium.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-mentioned problems. Provided is a magneto-optical recording medium in which abrasion and damage of the recording medium are prevented. That is, it is an object of the present invention to provide a magneto-optical recording medium of a magnetic field modulation type having excellent durability even under high-density recording conditions.

[0006]

The magneto-optical recording medium according to the present invention which solves the above-mentioned problems has a magneto-optical recording layer sandwiched between a substrate and a protective layer having irregularities on the surface. Is further provided with a lubricant layer containing a monoester obtained from an unsaturated alkyl carboxylic acid and a fluorinated alcohol. This lubricant layer is characterized by the fact that monoesters of unsaturated alkyl carboxylic acid and fluorinated alcohol reduce the friction between the magnetic head slider and the protective layer, and can significantly improve the durability of the magneto-optical recording medium. . Further, the height of the unevenness is set to 0.05 μm or more and 1 μm or less, the unevenness of the protective layer is provided at a rate of 1 or more and 20 or less per 1 μm square, and the thickness of the lubricant layer is set to 50 n.
m and 200 nm or less. Such a magneto-optical recording medium can more effectively reduce the friction coefficient of the magneto-optical disk, significantly improve the CSS characteristics, and open up the possibility of constant sliding with the magnetic head slider. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific structure of the magneto-optical recording medium of the present invention will be described. FIG. 1 is a schematic sectional view of a magneto-optical recording medium according to the present invention. In FIG. 1, 1 is a substrate,
3 is a magneto-optical recording layer, 2 and 4 are dielectric layers which are protective layers of the magneto-optical recording layer 3, 5 is a reflective layer, and 6 is a protective layer provided with irregularities on the surface by adding organic or inorganic particles. , 7 is a lubricant layer which is a feature of the present invention, 8 is a magnetic head slider,
9 is a laser beam. The lubricant layer 7 significantly reduces the friction and wear between the magnetic head slider 8 and the protective layer 6 of the magneto-optical recording medium, and can ensure the durability required for data use even in constant contact.

As the resin of the protective layer 6, a photocurable resin or a thermosetting resin can be used. For example, an ultraviolet curable acrylic resin, an epoxy resin, a polyene polyol resin or a thermosetting phenol resin, an epoxy resin, an acrylic resin, or a polyester resin can be used.

As particles for forming irregularities on the surface of the protective layer 6, inorganic particles such as alumina and silica, and organic particles such as Teflon (registered trademark) and acrylic can be used. In the present invention, the average particle diameter of these particles is 0.5 μm or more and 3 μm or less, and the compounding amount to the resin is 5 to 5.
Asperities are provided on the surface of the protective layer 6 as 50%. When the average particle diameter of the particles is 0.5 μm or less, the protective layer 6
Cannot form a protrusion of 0.05 μm or more on the surface of the substrate, resulting in a problem that the friction coefficient is increased. On the other hand, when the average particle diameter of the particles exceeds 3 μm, the protrusion on the surface of the protective layer 6 becomes 1 μm or more, and the density becomes 1 or less per 1 μm square, so that the CSS characteristics cannot be improved. Occurs.

Further, from the same viewpoint, it is preferable to set the thickness of the protective layer 6 to 5 to 20 μm. With this configuration, the density of the surface irregularities of the protective layer 6 is set to 1 to 2 per 1 μm square.
It can be zero. If the density of the surface irregularities of the protective layer 6 is less than one per 1 μm square, the load of the slider is received by the small projections, and the projections are easily broken, and the CSS characteristics cannot be improved. On the other hand, the density of the surface irregularities of the protective layer 6 is 20 μm per 1 μm square.
If the number exceeds the number, the number of contact points with the slider increases, and the friction coefficient increases. As a result, CSS
There is a problem that the characteristics cannot be improved. Therefore,
From such a viewpoint, the height of the surface irregularities is 0.05 μm.
m or more and 1 μm or less.

The lubricant layer 7 has a synergistic effect with the protective layer having the uneven surface to reduce wear from the magnetic head slider, and imparts the durability required for data to the magneto-optical recording medium of the present invention. This lubricant has a remarkable effect that a monoester compound of an unsaturated alkyl carboxylic acid and a fluorinated alcohol improves durability with a magnetic head slider. According to the findings of the inventors, diesters obtained from the reaction between a fluorinated dialcohol and an unsaturated alkyldicarboxylic acid or an unsaturated alkyldicarboxylic anhydride have little effect on reducing the coefficient of friction, and the durability of the magneto-optical recording medium is reduced. Not enough to improve the quality.

The thickness of the lubricant layer 7 is 10 nm or more and 200 n
m or less. When the thickness of the lubricant layer 7 is less than 10 nm, there is a problem that the amount of the lubricant is small, the effect of reducing the friction coefficient is small, and the durability of the magneto-optical recording medium is insufficient. On the other hand, if the thickness of the lubricant layer 7 exceeds 200 nm, the lubricant becomes excessive, and the protrusions on the surface of the protective layer are buried with the lubricant, causing a problem that the friction coefficient increases.

Next, a method for manufacturing the magneto-optical recording medium of the present invention will be described. First, a dielectric layer 2 is formed on a substrate 1 by vapor deposition or sputtering. The substrate 1 is not particularly limited, and a substrate made of glass, polycarbonate resin, acrylic resin, polystyrene resin, or polyolefin resin is used. Preforms such as tracking grooves and prepits may be formed on the surface of these substrates.

Next, a magneto-optical recording layer 3, a dielectric layer 4, and a reflective layer 5 are formed on the dielectric layer 2 by vapor deposition or sputtering.
There is no particular limitation on the magneto-optical recording layer 3, and GdTb, Td
bFe, GdTbFe, TbFeCo, GdTbFeC
and an amorphous, perpendicular magnetic recording layer such as o, and a laminated film of these. Further, it is preferable to protect the magneto-optical recording layer 3 mechanically, chemically as dielectric layer 2, SiO ₂ or S
i ₃ N ₄ or the like is used. Note that the dielectric layers 2 and 4
In this specification, the dielectric layer 2 closer to the substrate 1 may be referred to as a first dielectric layer, and the dielectric layer 4 farther from the substrate 1 may be referred to as a second dielectric layer.

As the reflection layer 5, Al, Ag, Au or the like is used. The protective layer 6 is formed by applying a predetermined amount of inorganic or organic particles to a monomer or prepolymer of a thermosetting resin or an ultraviolet curable resin described above with a bar coater, a spin coater, a roll coater, or the like, and heating or irradiating. Irradiate and cure.

The lubricant layer 7 is formed by dissolving a lubricant having the composition described above in a solvent capable of dissolving alcohol or the like, and then applying a predetermined concentration of the lubricant by a spin coater, bar coater, roll coater or the like. Thus, the magneto-optical recording medium according to the present invention is produced.

[0017]

Next, the present invention will be specifically described with reference to examples. A region having a radius of R22 to R42 mm on a polycarbonate resin disk substrate 1 having a thickness of 1.2 mm, an inner diameter of 15 mm, an outer diameter of 86 mm, and a track groove having a width of 0.5 μm and a pitch of 1.6 μm formed concentrically on one surface. Then, Si ₃ N ₄ is formed as a first dielectric layer 2 to a thickness of 110 nm.
Next, as the magneto-optical recording layer 3, a Gd-Fe-Co-Cr amorphous film and a Tb-Fe-Co-Cr amorphous film were formed to a total thickness of 30 nm.

Further, as a second dielectric layer 4, S
i ₃ N ₄ was formed to a thickness of 30 nm, and Al was provided thereon as a reflective film 5 to a thickness of 60 nm. All of these films were formed by a sputtering method.

Next, the Al ₂ O ₃ having an average particle diameter of 1.0μm to UV-curable resin composition 20% those obtained (weight ratio) is dispersed, the reflective layer 5 and on the substrate as shown in FIG. 1 The thickness is 1 by spin coating so that the inner and outer peripheries are in direct contact with the substrate.
5 μm and then UV lamp (wavelength 3
(65 nm) for 7 seconds to cure the resin. The height of the concavities and convexities on the surface of the protective layer 6 obtained as a result was 0.4 μm as measured by a stylus type measuring instrument, and the density of the concavities and convexities was 6 per μm square. At this time, the protective layer 6 having a thickness of 15 μm may be formed at a time. However, first, an ultraviolet curable resin containing no particles such as Al ₂ O ₃ is provided at 12 μm, and then an ultraviolet curable resin containing only 3 μm particles is used. When the protective layer 6 was formed, the reproducibility of the surface roughness and density could be improved.

The following composition was used as the UV-curable resin composition. Epoxy acrylate: 20 wt% Dimethylolpropane diacrylate: 65 wt% Trimethylolpropane triacrylate: 10 wt% Acetophenone photopolymerization initiator: 5 wt%

Next, a propanol solution of perfluorohexyl oleate (monoester of oleic acid and perfluorohexyl alcohol) adjusted to a concentration of 1 wt% is applied onto the protective layer 6 by a spin coater to form a 45 nm thick layer. The lubricant layer 7 was formed, and it was set as the sample 1.

When the concentration of the perfluorohexyl oleate solution in propanol is 2 wt%, the thickness of the lubricant layer 7 is 60 nm, and similarly, when the concentration is 3 wt%, the thickness of the lubricant layer 150 is 4 nm.
wt% is 200 nm.
And 4. Lastly, when the concentration of the propanol solution of perfluorohexyl oleate was 4.5 wt%, the thickness of the lubricant layer 7 was 250 nm. The magneto-optical recording medium in which the lubricant layer 7 was not formed was used as Sample 6.

The particles added to the UV-curable resin composition were Teflon particles having an average particle size of 0.1 μm to 2 μm, and the height of the surface of the completed protective layer 6 was changed. The thickness of the protective layer 6 is set to 10 μm, and the height of the surface irregularities is set to 0.03.
μm, 0.05 μm, 0.5 μm, 1.0 μm, 1.2
μm, and these are designated as Samples 7, 8, 9, 1 and 2, respectively.
0 and 11. A 2 wt% ethanol solution of pafluorooctyl linolenate was applied onto these samples by a spin coater to form a lubricant layer 7 of 80 nm.

Further, the particles to be added to the ultraviolet-curable resin composition are silica of 1 μm, and the surface roughness of the protective layer 6 is set to 0.1 μm.
5 μm, the density of surface irregularities was adjusted by the amount of silica particles added, and the number of irregularities was 0.8 per square micron.
2, 20, and 22, samples 12, 13, 1
4 and 15. A 3 wt% solution of perfluorodecyl oleate in propanol was applied on these samples with a spin coater to form a lubricant layer 7 having a thickness of 100 nm. A sample in which no particles were added to the ultraviolet-curable resin composition and the lubricant layer 7 was not provided was designated as Sample 16, and a 50-nm-thick perfluorohexyl oleate lubricant layer 7 was used.
The sample formed was used as Sample 17.

The static friction coefficients of the magneto-optical disks of Samples 1 to 17 were measured using a friction stiction tester (Minebea). Measurement conditions are ANSI X3B
The method of measuring the coefficient of friction between the magnetic head and the disk specified in 7/87 was followed. The results are shown in Table 1.

Further, when the magneto-optical discs of Samples 1 to 17 were rotated at 3000 rpm, the distance between the magnetic head slider of the magneto-optical disc recording / reproducing apparatus and the protective layer 6 was adjusted to 1.6 μm. 3000rpm
A CSS test was performed in which a series of operations of rotating at 3 rpm for 3 seconds and then stopping for 3 seconds was repeated. The results are also shown in Table 1.

[0027]

[Table 1]

As can be understood from Table 1, the height of the unevenness on the surface of the protective layer 6 is 0.05 μm or more and 1 μm or less, and the unevenness is formed at a rate of 1 or more and 20 or less per micron square. By providing a lubricant layer 7 having a thickness of 50 nm or more and 200 nm or less made of a monoester of an unsaturated alkyl carboxylic acid and a fluorinated alcohol on the protective layer 6, the friction coefficient of the magneto-optical disk is reduced, and the CSS characteristics are significantly improved. And the possibility of constant sliding with the magnetic head slider can be opened.

[0029]

According to the present invention, an optical disk which prevents abrasion and damage of a protective layer of a magneto-optical recording medium due to sliding between a magnetic head slider and a protective layer of the magneto-optical recording medium due to high density recording of a magneto-optical recording medium in the future. A magnetic recording medium is provided. That is, according to the present invention, a magneto-optical recording medium of a magnetic field modulation type having excellent durability even under high-density recording conditions is provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a magneto-optical recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 1st dielectric layer 3 Magneto-optical recording layer 4 2nd dielectric layer 5 Reflective layer 6 Protective layer 7 Lubricant layer 8 Magnetic head slider 9 Laser beam

Claims (2)

[Claims] 1. A magneto-optical recording medium in which a magneto-optical recording layer is sandwiched between a substrate and a protective layer having irregularities on the surface, wherein the protective layer is formed from an unsaturated alkyl carboxylic acid and a fluorinated alcohol. A lubricant layer containing a monoester to be provided, wherein the height of the unevenness is not less than 0.05 μm and not more than 1 μm, and the number of the unevenness is not less than 1 and not more than 20 per 1 μm square on the protective layer. And a thickness of the lubricant layer is not less than 50 nm and not more than 200 nm. 2. The method according to claim 2, wherein the protective layer comprises at least two layers: a first protective layer made of a resin containing particles forming the irregularities, and a second protective layer made of a resin not containing the particles. The magneto-optical recording medium according to claim 1, wherein the first protective layer is interposed between the protective layer and the lubricant layer.