JP2689672B2 - Manufacturing method of optical disk substrate - Google Patents

Description

The present invention relates to a method for manufacturing an optical disk substrate, and more particularly to a video disk, a CD or a CD-ROM dedicated to reading information, and a write-once optical disk capable of additionally recording information. The present invention relates to an optical disk substrate such as a rewritable optical disk in which information can be rewritten, and a manufacturing method thereof.

[Conventional technology]

A conventional optical disk substrate is manufactured by the process shown in FIG.

 Hereinafter, description will be made in order.

(A) In the glass disk manufacturing process, the surface of the glass disk 1 is polished and washed.

(B) In the photoresist applying step, the surface of the glass disk 1 which has been surface-polished and washed is coated with the photoresist 13,
This is dried.

(C) In the recording process using laser light, the information to be recorded is irradiated on the photoresist 13 applied to the glass disk 1 by the intensity modulation of the laser light 4 to perform exposure.

(D) In the developing step, the photoresist 13 is developed.
The photoresist 13 in the unexposed portion does not react in the developing treatment, and the photoresist 13 in the portion exposed by the laser beam 4 reacts in the developing treatment to form pits 14. The glass disk made in this way is called a glass master.

(E) In the plating step, the glass master is plated.
When the plated metal is peeled off, irregularities such as pits on the glass master are inverted and transferred. This is called stamper 15.

(F) In the molding step, the stamper 15 is used to transfer a plastic material such as polycarbonate by a technique such as injection molding or a photopolymer (2P) method to mold the optical disk substrate 16. At this time, since the unevenness of the stamper 15 is inverted and transferred, the unevenness of the finally molded optical disk substrate 16 matches the glass master.

On the optical disk substrate 16 manufactured as described above, a reflective film, a protective film, a recording film, etc. are formed according to the application of each optical disk.

FIG. 9 shows an example of a magneto-optical disk using the conventional optical disk substrate 16, which is a groove 19 for operating the tracking servo, and pits 17 for recording information such as tracking and sector addresses. An intermediate film 8, a magnetic recording film 9, and a protective film 10 are formed on an optical disk substrate 16 on which a substrate depression is formed. In such a conventional optical disk substrate 16, the pits 17 and the grooves 19 are formed with a substantially gentle curved surface, but the bottom of the pits 17 has an acute angle portion 18. The acute-angled portion 18 of the optical disc substrate 17 has an intermediate film 8, a recording film 9, and a protective film 10 formed on the optical disc substrate 16.
It also influences to form a steep gap. In an optical disc, if there are defects or dust that cause a gap in the medium, peeling or corrosion of the recording film or protective film tends to occur from that portion, and the acute angle portion 18 also tends to peel or corrode. To have.

The reason why such an acute angle portion 18 exists on the optical disc substrate 16 is due to the following manufacturing method.

As described above, the conventional optical disk substrate manufacturing process is
It is made by the process shown in FIG. FIG. 7 shows FIG. 6 (C).
Although it is an enlarged view of FIG. 3, laser light 4 is irradiated onto a glass master disk formed by coating a photoresist 11 on the glass disk 1 for recording. When this glass master is developed, it becomes as shown in FIG. Since the glass disk 1 is exposed in the pit 14, an acute angle portion is generated. From this glass master,
When an optical disk substrate is manufactured through the plating process (E) and the molding process (F) in FIG. 6, pits 17 as shown in FIG.
An acute angle portion 18 is generated at the bottom of the.

In the recording process with a laser beam of FIG. 6C, when a weak laser beam is irradiated so as not to expose the glass disk 1 and the developing process is performed, the edge of the pit becomes too gentle, and the reproduction signal intensity cannot be obtained. Moreover, the information recording density is also reduced. Therefore, the pit edge cannot be made smooth.

From the above, the conventional optical disc substrate manufacturing method could not produce an optical disc substrate without forming an acute angle portion in the pit portion.

[Problems to be solved by the invention]

However, such a conventional method for manufacturing an optical disk substrate has a drawback in that the recording film and the protective film are likely to be peeled off or corroded, resulting in lack of long-term reliability.

[Means for solving the problem]

(1) The optical disk substrate of the present invention is an optical disk substrate in which information is recorded with or without pits, and the bottom of the pits is formed with a curved surface without an acute angle.

(2) The optical disk substrate manufacturing method of the present invention is a method for manufacturing an optical disk substrate in which information is recorded by the presence or absence of pits.
It comprises a recording process by laser light, a developing process, a plating process, and a molding process, and is constituted by using two or more kinds of photoresists having different sensitivity characteristics in the photoresist coating process.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

 FIG. 1 is a manufacturing process diagram showing an embodiment of the present invention.

The optical disc substrate manufacturing method shown in FIG. 1 is different from the conventional optical disc substrate manufacturing process in the photoresist coating process, and includes a two-step process including a first photoresist coating process B1 and a second photoresist coating process B2.

FIG. 2 is a diagram in which the glass master after the completion of the first photoresist coating step B1 and the second photoresist coating step B2 is irradiated with laser light 4 for exposure. On the glass master,
The second photoresist layer 3 of the first photoresist layer 2 is laminated. The sensitivity characteristics of the second photoresist layer 3 of the first photoresist layer 2 are shown in FIG. This is irradiated with the laser beam 4 to be exposed. At this time, the exposure power of the laser beam 4 is such that the glass substrate 1 is not exposed by the pits 5 as shown in FIG. 4 after the development processing. As a result, the pit bottom has a gentle curved surface without an acute angle. At this time, since the exposure sensitivity of the second photoresist film 3 is higher than that of the first photoresist film 2, the edge of the pit can be made steep, so that unlike the conventional example, a sufficient reproduction signal strength is obtained. Can be obtained, and the recording density of information is not reduced.

From the glass master shown in FIG. 4 through the plating step E and the forming step F shown in FIG. 1, an optical disk substrate of a pit having a curved surface without an acute angle can be prepared according to the present invention.

FIG. 5 shows a sectional view of an embodiment in which a magneto-optical disk is formed by using the optical disk substrate according to the present invention.

On the optical disk substrate 7 according to the present invention shown in FIG. 5, a groove 12 for operating a tracking servo and a pit 11 for recording information such as a track or sector address are formed, and an intermediate film 8 and a magnetic recording layer are formed thereon. The film 9 and the protective film 10 are configured. At this time, since the pits 11 on the substrate do not have the acute-angled portions 18 as shown in FIG. 9, peeling or corrosion of the recording film or the protective film does not occur.

〔The invention's effect〕

The method for manufacturing an optical disk substrate of the present invention makes it possible to provide a substrate having no sharp corners at the bottom of the pits, so that peeling or corrosion of the recording film or protective film does not occur, and long-term reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram showing an embodiment of the present invention, FIG. 2 is a sectional view showing a glass master and a laser irradiation state in the recording process shown in FIG. 1, and FIG. 3 is each resist shown in FIG. FIG. 4 is a sensitivity characteristic diagram of the film, FIG. 4 is a cross-sectional view of the glass master after the developing process shown in FIG. 1, and FIG. 5 is a light produced by using an optical disk substrate manufactured through the manufacturing process shown in FIG. FIG. 6 is a sectional view of a magnetic disk, FIG. 6 is a manufacturing process diagram showing an example of a conventional method, FIG. 7 is a sectional view showing a glass master and a laser irradiation state in the recording process shown in FIG. 6, and FIG. 8 is FIG. The cross-sectional view of the glass master after the developing process shown in FIG.
FIG. 6 is a cross-sectional view of a magneto-optical disk manufactured using the optical disk substrate manufactured through the manufacturing process shown in the figure. G, G1 …… Glass master, 1 …… Glass disk, 2 …… First photoresist layer, 3 …… Second photoresist layer, 4 …… Laser light, 5,11,14,17 …… Pit, 6,15 ...... Stamper, 7,16
...... Optical disk substrate, 8 ... Intermediate film, 9 ... Magnetic recording film, 10 ... Protective film, 12,19 ... Groove, 13 ... Photoresist, 18 ... Acute angle part, A ... Glass disk manufacturing process, B1 ... first photoresist coating step, B2 ... second photoresist coating step, B ... photoresist coating step, C ... recording step, D ... developing step,
E ... Plating process, F ... Molding process, l ... Remaining film thickness, V ... Exposure amount.

Claims (1)

(57) [Claims] 1. A glass disk manufacturing process for manufacturing a glass disk, a first photoresist coating process for coating a first photoresist, and an exposure sensitivity higher than that of the first photoresist after the first photoresist coating process. A second photoresist coating step of applying a high second photoresist, a recording step of recording with a laser beam, a developing step of developing the recording, and a pit pattern formed by development on the glass disk. In a method of manufacturing an optical disk substrate, which includes a plating step of applying a step of forming an optical disk with a stamper formed by the plating, the recording step includes a constant step such that the first photoresist is not completely exposed. A method for manufacturing an optical disk substrate, which is performed with an exposure amount.