JPH09128805A - Optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the infiltrating of a coating liquid for spin coating to the rear surface of a disk, to make tracking normal and to eliminate hindrance to recording and reproducing by providing the end face of a disk substrate with a projecting body in an annular form. SOLUTION: Grooves for tracking are formed on one surface of the substrate 12 consisting of a polycarbonate resin to form a recording surface. The back coating surface of the substrate 12 is coated with a resin layer 5 at a uniform thickness by a spin coating method. The substrate 12 is provided with the projecting body 13a having the surface flush with the back coating surface of the substrate in the annular form on the end face near the back coating surface. As a result, the coating liquid is blocked by the projecting body 13a without arriving at the recording surface even if the coating liquid spreads to the outer side and tends to infiltrate to the recording surface side at the time of coating the substrate with the resin layer 5 by the spin coating method. The tracking is thereby made normal and the high quality and high reliability are embodied without the hindrance to recording and reproducing.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an improvement of an optical disc.

[0002]

2. Description of the Related Art There is a magneto-optical disk as one type of optical disk, which is already on the market. The structure of this magneto-optical disk will be described with reference to FIGS. FIG. 4 is a plan view of the magneto-optical disk M (diameter 3.5 inches), and FIG. 5 is a sectional view taken along the section line XX shown in FIG.

According to the magneto-optical disk M, a transparent disk substrate 1 made of a polycarbonate resin is used, and a large number of tracking grooves 2 are formed concentrically on one side of the disk substrate 1, and a central portion thereof is formed. Hub mounting hole 3
Is provided. The surface on which the tracking groove 2 is formed is covered with at least a thin film 4 made of a magneto-optical recording layer (hereinafter referred to as a recording surface), and the other main surface is for protecting the disk substrate 1. The resin layer 5 is formed by a spin coating method (hereinafter, the other main surface is referred to as a back coat surface).

This spin coating method will be described with reference to FIG. 6, in which 6 is a turntable and 7 is a turntable 6.
Is a rotary shaft for rotating the substrate, 8 is a substrate to be coated (corresponding to the magneto-optical disk M before coating the resin layer 5 in this example) arranged on the turntable 6, and 9 is a coating liquid. Is a nozzle for dropping onto the substrate 8 to be coated.

For spin coating, when the turntable 6 is rotated and the coating solution is dropped from above the center of the substrate 8 to be coated with a nozzle 9, the coating solution spreads outward, and the nozzle 9 also remains outside. The coating liquid is coated on the substrate 8 to be coated with a uniform thickness by moving to.

[0006]

However, when the resin layer 5 is formed by the spin coating method as described above, there is a problem that a part of the resin wraps around to the recording surface. This problem is shown in FIG. explain.

This figure is a plan view showing the recording surface of the magneto-optical disk M. Under the coating conditions, for example, a relatively large amount of the coating liquid is applied from the nozzle 9 or the rotation speed of the turntable 6 is reduced. In this case, when a part of the coating liquid wraps around the recording surface and is cured as it is, a wrap-around portion 10 and a streak-like portion 11 are formed as shown in the drawing, and therefore, when the magnetic drive is performed, the tracking works normally. There was a problem of disappearing.

Therefore, the object of the present invention is to prevent the resin from wrapping around to the back surface side of the resin layer formed by the spin coating method, thereby normalizing the tracking and preventing the recording / reproducing from being disturbed. It is to provide an optical disc of high quality and high reliability.

[0009]

The optical disk of the present invention comprises:
An optical recording layer is formed on one main surface of the disk-shaped substrate, and a resin layer is formed on the other main surface by a spin coating method.
Furthermore, on the end surface near the other main surface of the disk-shaped substrate,
It is characterized in that the convex body is provided in an annular shape.

[0010]

1 is a block diagram of a magneto-optical disk H of the present invention.
2 and FIG. 3 are enlarged cross-sectional views of the main part of the magneto-optical disk H, respectively. The same parts as those of the magneto-optical disk M are designated by the same reference numerals.

According to the magneto-optical disk H, a substrate 12 made of a polycarbonate resin is used as a transparent disk substrate, and a large number of tracking grooves 2 are concentrically formed on one surface side (recording surface) of the substrate 12. A hub mounting hole 3 is provided at the center. Tracking groove 2
A thin film 4 is coated on the surface on which is formed.

The thin film 4 is, for example, a dielectric layer made of sialon, a magneto-optical recording layer made of an alloy of a rare earth metal and a transition metal for recording and erasing information, a dielectric layer made of sialon, and a reflection made of aluminum. It is a laminated structure of a layer and a protective resin layer.

The resin layer 5 is coated on the back coat surface by the conventional spin coating method. That is,
As shown in FIG. 6, the turntable 10 is rotated to apply the coating liquid with the nozzle 13 from above the vicinity of the center of the substrate 10 to be coated, and when the nozzle 13 also moves to the outside, the coating liquid moves to the outside. The coating solution spreads and is coated on the substrate 12 to be coated with a uniform thickness.

Then, the convex body 13 is provided in an annular shape on the end face of the substrate 12 near the back coat surface. As an example of providing the convex body 13, as shown in FIG. 2, the convex body 1 having a surface aligned with the back coat surface.
3a and a convex body 13b having a slight step difference from the back coat surface.

Thus, in the magneto-optical disk H having the above structure, the convex body 13 is formed on the end face near the back coat surface.
Since the a and 13b are provided in a ring shape, when the resin layer 5 is coated by the above spin coating method, even if it goes around, it is blocked by the convex bodies 13a and 13b, thereby reaching the recording surface. Disappear. In addition, in the present invention, in addition to the convex bodies 13a and 13b having these shapes, a plurality of convex bodies 13a may be provided at these formation sites to obtain the same operational effect.

[0016]

EXAMPLES When a magneto-optical disk H having a diameter of 3.5 inches was used and applied under the spin coating conditions as described below, the rotation speed of the turntable 10 was 100 to 100.
At 300 rpm, the coating liquid did not reach the recording surface at all.

However, in the magneto-optical disk H provided with the convex body 13a, the height of the convex body 13a is 0.2 mm.
I made it. In addition, a magneto-optical disk H provided with a convex body 13b
For, the height of the convex body 13b is set to 0.1 mm,
The step was set to 0.1 mm.

Spin coating conditions Viscosity of coating liquid: 66 cp Surface tension of coating liquid: 35 dyn / cm Coating thickness: 4 to 15 μm Rotation speed during coating: 100 to 300 rpm Rotation speed of shake-off (excessive amount on substrate surface after coating) Rotation speed when shaking off the resin): 3000-4500 rpm Coating pressure (pressure at which the resin is coated on the substrate surface): 3 kg /
cm ^2, however, the convex body 13a, without forming a 13b,
When the conventional magneto-optical disk M having the same other constitution was applied under the same spin coating conditions, the results shown in Table 1 were obtained.

In the table, ◯ indicates that the coating liquid did not wrap around, and X indicates that the coating liquid wraps around.

[0020]

[Table 1]

As is clear from these results, in the present invention, even under the conventional conditions where the coating liquid wraps around,
You can see that there is no wraparound.

The present invention is not limited to the above embodiments, and various modifications and improvements can be made without departing from the scope of the present invention. For example, an optical disk such as a CD-ROM, a CD-R, or a CD, instead of the magneto-optical disk, has the same effect.

[0023]

As described above, in the optical disc of the present invention, the coating solution for spin coating is provided on the back side of the coating surface by providing the convex body in an annular shape on the end surface of the disk-shaped substrate. It is possible to provide an optical disk of high quality and high reliability in which the tracking does not occur and the tracking is made normal so that recording and reproduction are not hindered.

[Brief description of the drawings]

FIG. 1 is a sectional view of a magneto-optical disk H of the present invention.

FIG. 2 is an enlarged sectional view of an essential part of a magneto-optical disk H of the present invention.

FIG. 3 is an enlarged sectional view of an essential part of a magneto-optical disk H of the present invention.

FIG. 4 is a plan view of a conventional magneto-optical disk M.

FIG. 5 is a sectional view of a conventional magneto-optical disk M.

FIG. 6 is an explanatory diagram of a spin coating method.

FIG. 7 is a rear view of a conventional magneto-optical disk M.

[Explanation of symbols]

 M, H Magneto-optical disk 1, 12 Substrate 2 Tracking groove 4 Thin film 5 Resin layer 13, 13a, 13b Convex body

Claims (1)

[Claims] 1. An optical disk comprising an optical recording layer formed on one main surface of a disk-shaped substrate and a resin layer formed on the other main surface by a spin coating method, wherein a convex body is provided on an end surface of the disk-shaped substrate. On the other hand, an optical disk characterized by being provided in a ring shape near the main surface.