JPH05342656A - Optical recording medium - Google Patents

Abstract

PURPOSE:To provide an optical recording medium capable of avoiding the sticking of a magnetic head to the medium by forming protrusions uniform in height at equal pitches on a protective layer for protecting the magneto- optical recording layer of an optical recording medium. CONSTITUTION:Protrusions are formed on a protective layer in the form of nearly concentric circles or in a spiral shape. They are formed in a prescribed cross-sectional shape by roughening the surface of the protective layer with a machining tool. The average height of the protrusions is 0.11-0.5mum and their dispersion is <=0.01mum.

Description

Detailed Description of the Invention

[0001]

The present invention relates to recording with a light beam,
The present invention relates to a protective layer of an optical recording medium capable of reproducing and erasing, and particularly to a protective layer of a magneto-optical recording medium capable of overwriting (overwriting) by a magnetic field modulation method.

[0002]

2. Description of the Related Art Conventionally, as an overwritable magneto-optical disk and its apparatus, for example, JP-A-51-10 is available.
7121, JP-A-63-217548, JP-A-59
As described in JP-A-215008 and JP-B-60-48806, there is known a method of modulating the magnetic field applied to the magneto-optical recording layer according to the information to be recorded. In a magneto-optical recording system capable of overwriting by the magnetic field modulation method, it is necessary to keep a small gap (spacing) between the magnetic head and the magneto-optical disk constant. Therefore, smoothing of the surface protective layer of this disk was also desired. In addition, the surface roughness of the slider of the magnetic head is similarly finished to be super smooth. However, if the surface of the medium and the surface of the magnetic head slider are smoothed in this way, when such a medium is incorporated in the magneto-optical recording / reproducing apparatus, the magnetic head and the medium are stuck (adhesion phenomenon) when stopped. ), Causing serious damage to the head and the medium with rotation.

Therefore, the surface of the medium is roughened.
Texturing is, for example, a magazine (IEEE TRANS
ACTIONS ON MAGNETICS, Vol. Mag-23, No.5, September
1987, p.3405-3407).

FIG. 2 is a part of a radial cross-sectional view showing the surface roughness of the protective layer of the conventional example.
The magnification is 0 times and the magnification in the radial direction is 2,000 times.

[0005]

In the conventional medium in a magnetic field modulation type overwritable magneto-optical recording system, the surface of the protective layer film has an irregular distribution of irregularities as shown in FIG. Therefore, the actual contact area with the magnetic head slider is not constant, and there is a problem that there is a portion with a large contact area. At that position, there is a problem that a large adhesive force is generated while the rotation of the medium is stopped, and it becomes impossible to rotate the spindle motor.

An object of the present invention is to provide a sticking portion of a magnetic head and a magneto-optical recording medium by providing protrusions having a uniform pitch and a uniform height on the protective layer in order to solve the problems of the prior art. It is to provide a medium capable of avoiding (adhesion phenomenon).

[0007]

The optical recording medium of the present invention is characterized in that the protective layer has projections formed in substantially concentric or spiral shapes at substantially the same height.

It is preferable that the projections are formed by roughening the surface of the protective layer with a cutting tool to form a substantially predetermined cross-sectional shape at a uniform pitch in the radial direction. Furthermore, the projections have an average height. Is preferably in the range of 0.11 μm to 0.5 μm and has a variation of 0.01 μm or less.

[0009]

The protective layer of the optical recording medium according to the present invention is one in which concavities or spirals are roughened at a uniform pitch and the heights of the protrusions at a uniform pitch are made uniform.
The protective layer is roughened with a cutting tool made of, for example, diamond or a material having a hardness equivalent to that of the surface at a uniform pitch and the heights of the protrusions are equalized. Since it is possible to make it constant also in the above, it is possible to reduce the adhesive force between the head and the medium depending on the position and to reduce the variation thereof.

[0010]

EXAMPLES Next, three examples of the optical recording medium of the present invention will be compared with four comparative examples, and the first example will be described with reference to the drawings.

FIG. 1 is a part of a radial cross-sectional view showing the roughness of the surface of a protective layer of an optical recording medium according to an embodiment of the present invention. The magnification is 2,000 times. The manufacturing processes of three examples and four comparative examples will be described below, and the surface roughness of these products, the adhesion of the magnetic head, and the result of the CSS test will be described using Table 1.

(1) Example 1 First, a layer thickness of 1500 angstrom (0.1) was formed on a polycarbonate substrate having a guide groove and / or a preformat signal and having a thickness of 1.2 mm by a sputtering method.
5 μm) of Si ₃ N ₄ layer and then layer thickness 200
Angstrom (0.02 μm) amorphous Tb-Fe
A Co layer is laminated to provide a magneto-optical recording layer, and the layer thickness is 400
A Si ₃ N ₄ layer having an angstrom (0.04 μm) is formed, and a layer thickness of 700 angstrom (0.07 μm).
The Al layer of m) was formed.

Next, an ultraviolet curable urethane acrylate resin composition (SPC-339 manufactured by Nippon Kayaku Co., Ltd.) was spin-coated (4000 rpm, 10 seconds) to give a layer thickness of 10
After making the resin layer of μm, UV lamp (23
3 mW / cm ² , wavelength 365 mm) for 7 seconds,
The resin was cured to form a resin protective layer, and a provisional optical recording medium was obtained.

Further, the medium is rotated at 600 revolutions per minute, and a diamond cutting tool (section tip radius of curvature of 3 μm) is pressed against the surface of the medium while being 6 m in the radial direction of the substrate.
By moving at a speed of m / min, flaws that are almost concentric circles were formed, and the optical recording medium of this example was obtained.

(2) Comparative Example 1 Instead of the cutting step of the protective layer surface, which is the final step in the manufacturing process of Example 1, the protective layer surface was polished with a tape (WA # 200).
It is the medium obtained through the texturing process in 0).

(3) Comparative Example 2 This is a medium obtained without cutting the protective layer surface, which is the final step in the manufacturing process of Example 1.

(4) Comparative Example 3 In the manufacturing process of Comparative Example 2, S was used as the ultraviolet curable resin composition.
A medium obtained by using a mixture of i) 100 parts of the same resin and ii) 20 parts of alumina (AKP103) in place of the product of PC-339 Nippon Kayaku Co., Ltd.

(5) Example 2 This is a medium obtained by replacing the radius of curvature of the tip of the cutting tool of 3 μm in the cutting tool used in Example 1 with 4 μm.

(6) Example 3 This is a medium obtained by substituting 5 μm for the radius of curvature of the tip of the cutting edge of the cutting tool used in the production of Example 1.

(7) Comparative Example 4 This is a medium obtained by substituting 10 μm for the radius of curvature of the tip of the cutting edge of the cutting tool used in the production of Example 1.

Surface roughness (R
z) and head adhesion (g) are 20 for each side.
It was measured at several places. This head adhesion force measuring method is a method of measuring the force required to move the slider on the disk parallel to the disk surface when a spring load of 5 g is applied to the slider.

The method of measuring the depth of flaws on the medium surface is as follows: the magnetic head is levitated by 1.6 μm in 3 seconds from the state where the floating magnetic head is in contact with the medium surface and the medium is 2400 rpm.
And then spin the medium at 2400 for 3 seconds.
The magnetic head is brought into contact with the medium surface by reducing the rpm and then stopping. The depth of the flaw was measured after the CSS test in which this was repeated 1,000,000 times. Table of these results
Shown in 1.

[0023]

[Table 1] As can be seen from this, the average values of the surface roughness are almost the same in Example 1 and Comparative Example 1, but the variation in 20 points is smaller in Example 1. Also in terms of adhesion, Comparative Example 1
Is large, but in Example 1 it is quite small. Further, in Comparative Example 2, the adhesive force is much larger than in Example 1 and Comparative Example 1. In addition, since the flaw depth of the medium surface after the CSS test 1,000,000 times is also small in the first embodiment, the first embodiment is used in terms of prevention of sticking and head crash.
Is significantly superior to Comparative Examples 1, 2, and 3. In Examples 2 and 3 and Comparative Example 4, the absolute value of the surface roughness is large, but the variation is not so different from Example 1. The adhesive force and the depth of flaws after the CSS test are almost the same as those in Examples 2 and 3. As a whole, the comparative example is significantly larger than the example. From these results, it is understood that in the case of Examples 1, 2 and 3, favorable results are obtained and the object of the present invention is achieved.

The roughening of the protective layer with a cutting tool is
It suffices if it is applied to at least the area where CSS is performed on the surface. Further, the projection height can be further made uniform by polishing the surface of the roughened medium of the present invention.

[0025]

As described above, according to the present invention, the protective layer of the optical recording medium is roughened at a uniform pitch,
By making the heights of the protrusions represented by a uniform pitch uniform and eliminating the variation in the distribution, it is possible to suppress the variation in the head adhesion force due to the position of the protective layer surface and prevent the occurrence of head crush. effective.

[Brief description of drawings]

FIG. 1 is a part of a radial cross-sectional view showing the roughness of the surface of a protective layer of an optical recording medium according to an embodiment of the present invention, wherein a height expansion ratio is 200,000 times and a radial expansion ratio is 2 It is displayed at 1,000 times.

FIG. 2 is a part of a radial cross-sectional view showing the roughness of the surface of a protective layer in a conventional example, which is displayed at a magnification ratio of 200,000 times in height and a magnification ratio in radial direction of 2,000 times. .

Claims (3)

[Claims] 1. An optical recording medium comprising at least a magneto-optical recording layer on a disc-shaped substrate, and a protective layer formed on the recording layer, wherein the protective layer is substantially concentric or spiral. An optical recording medium having protrusions formed at substantially the same height. 2. The optical recording medium according to claim 1, wherein the protrusions are formed by roughening the surface of the protective layer with a cutting tool to form a substantially predetermined cross-sectional shape at a uniform pitch in the radial direction. . 3. The protrusions have an average height of 0.11 μm.
To 0.5 μm, and the variation is 0.
The optical recording medium according to claim 1, wherein the optical recording medium is formed so as to have a thickness of 01 μm or less.