JPH0877601A - Optical disk and fabrication thereof - Google Patents

Abstract

PURPOSE: To enable the improvement of ununiformity of reflectivity by improving byte error rate without deteriorating corrosion reliability even if a recording layer is formed without using external circumference mask. CONSTITUTION: A magneto-optical disk is constituted in such a manner that end face of external circumference 1a of the transparent substrate 1 of the disk is tapered and disk diameter D1 in the side of film forming surface 2 is set larger than the disk diameter D2 in the side of the reading surface 3. The facing part 21 of which external circumference 21a is tapered is provided on a pallet 11 and it is engaged without any clearance with the transparent substrate 1 of such magneto-optical disk to form a recording layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk, for example, a magneto-optical disk, one main surface of which is a film-forming surface on which a recording layer is formed and the other main surface of which is a reading surface.
Furthermore, it relates to a manufacturing method thereof.

[0002]

2. Description of the Related Art Recently, an optical disk has been drawing attention as a small-sized and large-capacity data storage medium. There are various types of optical discs having a diameter of 300 mm to 2.5 inches, and a read-only type and a recordable and reproducible type are commercially available.

As a read-only optical disc, one in which a metal such as Al or Au is laminated on one main surface to form a film-forming layer is generally used, and a substrate is formed by a thin film forming technique such as a vacuum deposition method or a sputtering method. It is formed by laminating on top. Further, as an optical disk for recording / reproducing, there are a magneto-optical disk, a phase change disk, a write-once disk capable of recording only once, and the like.

In the magneto-optical disk, a rare earth-transition metal alloy is generally used as the material for the recording layer, and this alloy film has a multi-layer structure sandwiched between a dielectric film and a reflective film. Each of the multilayer films is formed by laminating on the substrate by the thin film forming technique described above. Further, in the above optical disc, whether it is for reproduction only or for recording / reproduction,
In many cases, a protective film is formed by applying an ultraviolet curable resin or the like on the recording layer by a spin coating method.

By the way, when a recording layer is formed on the substrate to manufacture an optical disk, a film forming apparatus as shown in FIG. 4 is used. This film forming apparatus is provided with an optical disk substrate 101.
And a peripheral mask 103 and an outer peripheral mask 104 that cover the vicinity of the inner peripheral edge and the outer peripheral edge of the one main surface which is the film formation surface of the substrate 101.

At the time of film formation, first, the substrate 101 is placed and fixed on the pallet 102 using the inner peripheral mask 103 and the outer peripheral mask 104 via the disk base 105. In this state, a recording layer is formed by the thin film forming technique described above, and the inner peripheral mask 103 and the outer peripheral mask 10 are further formed.
4 is removed and the protective film is formed on the entire one main surface of the substrate 101 on which the recording layer is formed.

As described above, when the recording layer is formed,
Since the inner peripheral mask 103 and the outer peripheral mask 104 are used, inevitably, non-film-forming portions of the recording layer are formed near the inner peripheral edge and the outer peripheral edge of the substrate. Therefore, during the formation of the protective film, the recording layer can be completely covered, and the UV curable resin and the substrate surface are directly adhered to each other at the non-deposited portion, and the recording layer is damaged. And corrosion is prevented, improving the reliability of the product.

[0008]

However, when the recording layer is formed, the substrate 101 is placed on the pallet 10.
When the optical disc is mounted on the optical disc 2, the inner peripheral mask 103 and the outer peripheral mask 104 are likely to generate dust, which causes an increase in the error rate of the manufactured optical disc, and the film thickness is not stable near the mask edge. There are problems such as large fluctuations in reflectance.

Further, as the recording layer is repeatedly formed, the material of the recording layer is gradually deposited on each mask, and this deposit is peeled off to become the main cause of dust generation. It is costly to replace each mask with a new one.

Further, since the mounting of each mask is a complicated work, a mounting error is likely to occur, which causes a large decrease in yield and operating rate.

Therefore, in consideration of the fact that the inner peripheral mask 103 is an indispensable member, when the recording layer is formed without using the outer peripheral mask 104, the recording layer cannot be completely covered, and corrosion is prevented. This leads to a decrease in reliability. Further, there is a concern that the adhesion of the protective film may be deteriorated because the non-deposited portion such as the recording film is not formed and there is no direct bonding between the ultraviolet curable resin and the substrate surface.

The present invention has been made in view of the above-mentioned problems, and even if a recording layer is formed without using an outer peripheral mask, the error rate is improved without degrading the corrosion reliability, and the reflectance fluctuation is suppressed. (EN) An optical disk and a manufacturing method thereof that can be improved and can greatly improve the yield of products by eliminating the mounting error etc. accompanying the mounting of the peripheral mask on the substrate because the peripheral mask is not used. The purpose is to provide.

[0013]

An object of the present invention is an optical disk in which one main surface side of a substrate is a film forming surface on which a recording layer is formed, and the other main surface side is a reading surface.
This is a method of manufacturing this optical disc.

According to the present invention, the outer peripheral end surface of the substrate is chamfered to be tapered, and the optical disk is constructed so that the disk diameter on the film forming surface side is larger than the disk diameter on the reading surface side. It is a thing.

At this time, the disk diameter on the reading surface side of the substrate is added to the circular diameter drawn by the outermost peripheral access position of the optical pickup of the optical disk device to be used with respect to the optical disk and the light spot diameter on the reading surface. It is desirable to configure the optical disc so that it is larger than the value.

Here, the optical spot diameter of the laser beam on the recording layer in the optical system generally used for the optical disc is 1 μm.
Although it is about m, the laser beam is condensed through the substrate, so that the light spot diameter is about 1 mm on the reading surface. At this time, in order for the laser light to be normally focused on the recording layer, the optical axis of the laser light needs to be perpendicular to the reading surface. Therefore, it is necessary to prevent the tapered outer peripheral end surface of the substrate from entering the light spot on the reading surface. From this point of view, a value obtained by adding the radius drawn by the outermost peripheral access position and the radius of the light spot, that is, the radius of the disc on the reading surface side of the substrate from the radius of the outermost position that the light spot can reach on the reading surface. Is preferably large.

In the present invention, the above optical disk is mainly a magneto-optical disk.

Further, according to the present invention, the substrate of the above-mentioned optical disk is placed on a pallet using an inner peripheral mask to cover the vicinity of the inner peripheral edge of one main surface which is a film forming surface, and the recording layer is formed on the film forming surface of this substrate. The manufacturing method of an optical disk for forming a film is targeted.

That is, in the present invention, the pallet is provided with a countersunk portion, the depth of the countersunk portion is made equal to or larger than the thickness of the substrate, and the substrate is fitted and fixed in the countersunk portion to form the recording layer. It is characterized by.

At this time, it is desirable that the counterbore be formed by forming a tapered outer peripheral portion. Here, it is preferable to form the outer peripheral portion of the counterbore portion so that the outer peripheral end surface is engaged with the substrate of the optical disk having a tapered shape without a gap.

[0021]

In the optical disk according to the present invention, the outer peripheral end surface of the substrate is chamfered to be tapered, and the disk diameter dimension on the film forming surface side is larger than the disk diameter dimension on the reading surface side.

Therefore, when the thin film forming technique is applied without forming the outer peripheral mask when forming the recording layer, the recording layer is formed on the entire one main surface of the substrate which is the film forming surface. Moreover, since the outer peripheral edge faces the reading surface side, which corresponds to the back surface of the film formation surface, the material of the recording layer is prevented from adhering to the outer peripheral edge. As a result, when the protective film is formed on the recording layer by spin coating or the like after the recording layer is formed, the protective film is the non-deposited portion when the recording layer is formed. Since the film is also formed on the end face, the recording layer is completely covered with the protective film, and the substrate and the protective film are bonded and adhere to each other at the outer peripheral end face.

Further, in the present invention, the pallet is provided with a countersunk portion, the depth of the countersunk portion is made equal to or larger than the thickness of the substrate, and the substrate is fitted and fixed in the countersunk portion to form the recording layer.

That is, when the recording layer is formed, the substrate of the optical disc is fitted and fixed in the countersunk portion, so that the depth of the countersunk portion is equal to or larger than the thickness of the substrate, so that the substrate is placed in the countersunk portion. The recording layer is completely embedded, and the recording layer is not formed on the outer peripheral end face, which is a non-deposited portion. When the substrate is removed from the counterbore and a protective film is formed by a method such as a spin coating method, the recording layer is completely covered with the protective film and the film can be formed up to the non-film-forming portion. It will be possible.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical disc and a method of manufacturing the same according to the present invention will be described below in detail with reference to the drawings showing specific embodiments applied to a magneto-optical disc.

The magneto-optical disk of the present embodiment has a recording layer (here, Si) on one main surface of a transparent substrate which is a disk substrate.
(N, TbFeCo, SiN, and Al are sequentially laminated) is sputtered, and an ultraviolet curable coating material such as UV resin is applied onto the recording layer by spin coating to form a protective film. A film-forming surface is formed and configured. Here, the back surface of the film formation surface is a reading surface on which a light spot is irradiated.

And, in particular, the magneto-optical disk is shown in FIG.
As shown in FIG. 5, the outer peripheral end surface 1a of the transparent substrate 1 is tapered, and the disk diameter dimension D1 on the film forming surface 2 side is larger than the disk diameter dimension D2 on the reading surface 3 side (D1> D2). ing.

Further, in the magneto-optical disk, the disk diameter dimension D2 on the reading surface 3 side is the circular diameter dimension d1 drawn by the outermost peripheral access position of the optical pickup of the magneto-optical disk device to be used with respect to the magneto-optical disk and the reading surface. Greater than the value obtained by adding the light spot diameter dimension d2 above (D
2> d1 + d2).

This is because of the following reasons. That is, the optical spot diameter of the laser beam on the recording layer in the optical system generally used for the magneto-optical disk is 1 μm.
Although the laser light is focused through the transparent substrate 1, the light spot diameter is about 1 mm on the reading surface 3. At this time, in order for the laser light to be focused normally, the optical axis of the laser light (indicated by a broken line L in the drawing) needs to be perpendicular to the reading surface 3. Therefore, it is necessary to prevent the tapered outer peripheral end surface 1a of the transparent substrate 1 from entering the light spot on the reading surface 3. From this point of view, the radius r1 (= d1 / 2) drawn by the outermost peripheral access position and the radius r2 (= d2) of the light spot.
/ 2), that is, the radius R2 (= D2 / 2) of the disk on the reading surface 3 side of the transparent substrate 1 from the radius of the outermost position where the light spot can reach on the reading surface.
Is preferably large (R2> r1 + r2).

When a recording layer is formed on the transparent substrate 1 to produce the magneto-optical disk, a film forming apparatus as shown in FIG. 2 is used. This film forming apparatus is composed of a pallet 11 on which a transparent substrate 1 of a magneto-optical disk is placed, and an inner peripheral mask 12 which covers the vicinity of the inner peripheral edge of one main surface which is the film forming surface 2 of the transparent substrate 1. ing.

Here, the pallet 11 is the transparent substrate 1
A counterbore portion 21 for fitting and fixing is provided, and the depth T of the counterbore portion 21 is equal to or larger than the thickness t of the substrate (T ≧ t).
And is configured.

The counterbore portion 21 has an outer peripheral portion 21a formed in a tapered shape, and is configured to engage with the transparent substrate 1 of the magneto-optical disk whose outer peripheral end surface 1a is tapered without a gap. There is.

At the time of film formation, first, the transparent substrate 1 is fitted and fixed in the spot facing portion 21 of the pallet 11 using the inner peripheral mask 12. In this state, a recording layer is formed by a sputtering method, the inner peripheral mask 12 is removed, and a protective film is formed by a spin coating method over the entire one main surface of the transparent substrate 1 on which the recording layer is formed.

According to the above-mentioned spin coating method, after the ultraviolet curable coating material such as UV resin is dropped on the magneto-optical disk, the magneto-optical disk is rotated at a high speed so that the coating material becomes a magneto-optical disk. Spread over the surface,
The protective film 3 having a uniform film thickness is formed.

As described above, in this embodiment, the outer peripheral end surface 1a of the transparent substrate 1 is tapered, and the disk diameter dimension D1 on the film forming surface 2 side is the disk diameter dimension D on the reading surface 3 side.
Greater than two.

Therefore, when a thin film forming technique such as a sputtering method or a vacuum deposition method is applied without forming an outer peripheral mask when forming the recording layer, the whole one main surface of the transparent substrate 1 to be the film forming surface 2 is formed. Since the recording layer is formed on the outer peripheral end surface 1a and the outer peripheral end surface 1a faces the reading surface 3 side which is the back surface of the film forming surface 2, the material of the recording layer is prevented from adhering to the outer peripheral end surface 1a. As a result, when the protective film is formed on the recording layer by spin coating or the like after the recording layer is formed,
Since the protective film is also formed on the outer peripheral end face 1a where the recording layer is not formed when the recording layer is formed, the recording layer is completely covered with the protective film and is protected from the transparent substrate 1. The film and the outer peripheral end face 1a are bonded and closely adhered to each other.

During film formation, the transparent substrate 1 is fitted and fixed in the countersunk portion 21 so that the countersunk portion 2 is formed.
Since the depth T of 1 is equal to or larger than the thickness t of the transparent substrate 1, the transparent substrate 1 is completely embedded in the spot facing portion 21, and no recording layer is formed on the outer peripheral end face 1a. It will be a film formation location. Then, when the transparent substrate 1 is removed from the countersunk portion 1a and a protective film is formed by a method such as a spin coating method, the recording layer is completely covered with the protective film and the film is formed up to the non-film-forming portion. It becomes possible.

Here, one experimental example will be described.
In this experiment, the error rate and reflectance of the magneto-optical disk sample 1 manufactured as described above were measured.

The transparent substrate 1 of the sample 1 on which the film is formed is
The thickness t is 1.2 mm, and the diameter D1 on the film formation surface 2 side is 65.
mm, the diameter D2 on the side of the reading surface 3 is 64 mm, and the circular diameter dimension d1 drawn by the outermost peripheral access position is 31 mm.

Further, as the film forming apparatus, the one in which the depth T of the spot facing portion 21 of the pallet 11 is 1.2 mm was used.

Here, as a comparative example to the above-mentioned embodiment, the same experiment as the above-mentioned experiment example was conducted using a conventional magneto-optical disk. First, in Comparative Example 1, a sample 2 of a magneto-optical disk in which a film was formed on a substrate 101 of a conventional magneto-optical disk whose outer peripheral end surface is not tapered by using a conventional film forming apparatus and an outer peripheral mask 104. Using. Next, in Comparative Example 2, Sample 3 manufactured in the same manner as in Comparative Example 1 was used except that the outer peripheral mask 104 was not used.

First, as Experiment 1, each of the samples 1 to
3 under the environment of a temperature of 85 ° C and a humidity of 95%.
The error rate was measured during the time-driven acceleration reliability test. In this measurement, a random EFM signal was recorded by a magnetic field modulation method at a linear velocity of 1.22 m / sec, a recording laser power of 4.55 mW, and a magnetic field of 24 kA / m, and then reproduced at a reproduction power of 0.6 mW to measure the number of errors. This is a study of changes.

The results of this experiment 1 are shown in FIG. In Sample 2, since the recording layer was formed using the outer peripheral mask 104, no deterioration was observed even after 200 hours, but it is hard to say that the initial value is a good value. Moreover, in Sample 3, the initial value is excellent because the outer peripheral mask 104 is not used, but it shows a significant deterioration over time. On the other hand, Sample 1 showed an excellent initial value and showed almost no deterioration even after 200 hours.

From this, it can be seen that the magneto-optical disk of the present embodiment has a significantly improved error rate as compared with the conventional one, and has more excellent durability.

Next, as Experiment 2, a laser wavelength of 780
The reflectance variation was measured using the nm optical system. As a result, Sample 2 showed a large variation of 3.5% due to the use of the peripheral mask 104, whereas Sample 3 showed an excellent value of 0.9%. Sample 1 showed a low variation value of 1.2%, which is almost the same as sample 3, because the peripheral mask was not used.

From this, it can be seen that the magneto-optical disk of this example exhibits a stable reflectance.

In the present embodiment, the magneto-optical disk has been described as an example of the optical disk, but the present invention is not limited to this, and other optical disks having a protective film on the recording layer, such as read-only optical disks and Of course, it can be applied to a phase change disc, a write-once disc, etc.

[0048]

As is apparent from the above, according to the present invention, even if a recording layer is formed on a substrate of an optical disk without using a peripheral mask, the error rate is improved without degrading the corrosion reliability. As a result, it is possible to improve the fluctuation of the reflectance, and since the peripheral mask is not used, there are no mounting mistakes due to the mounting of the peripheral mask on the substrate, and it is possible to significantly improve the yield of products.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a magneto-optical disk according to an embodiment.

FIG. 2 is a cross-sectional view that schematically shows how the recording layer is formed on the substrate of the magneto-optical disk of this example.

FIG. 3 is a characteristic diagram showing a change in error rate over time when an accelerated reliability test is performed on the magneto-optical disk.

FIG. 4 is a cross-sectional view that schematically shows how a recording layer is formed on a substrate of a conventional magneto-optical disk.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 1a Outer peripheral end surface 2 Deposition surface 3 Reading surface 11 Pallet 12 Inner peripheral mask 21 Spot facing 21a Outer peripheral portion

Claims (5)

[Claims] 1. An optical disc having one main surface side of a substrate as a film forming surface on which a recording layer is formed and the other main surface side as a reading surface, wherein the outer peripheral end surface of the substrate is chamfered and tapered. An optical disc characterized in that the disc diameter on the film-forming surface side is larger than the disc diameter on the reading surface side. 2. The disk diameter dimension on the reading surface side of the substrate is obtained by adding the circle diameter dimension drawn by the outermost peripheral access position of the optical pickup of the optical disc apparatus used to the optical disc and the light spot diameter dimension on the reading surface. The optical disc according to claim 1, which is large. 3. The optical disk according to claim 1, which is a magneto-optical disk. 4. The optical disk substrate according to claim 1 is placed on a pallet using an inner peripheral mask to cover the vicinity of the inner peripheral edge of one main surface which is a film forming surface, and recording is performed on the film forming surface of this substrate. A method for manufacturing an optical disk, characterized in that when forming a layer, a counterbore portion is provided on the pallet, the depth of the counterbore portion is made equal to or greater than the thickness of the substrate, and the substrate is fitted and fixed in the counterbore portion. 5. The method of manufacturing an optical disk according to claim 4, wherein the counterbore portion has a tapered outer peripheral portion.